Cactus casino: What the Brand Refers To and What UK Players Should Know

What Cactus Casino refers to

Cactus Casino is an online gambling platform operated by Ferzo Holding Limitada, a company registered in Costa Rica. The site holds a licence issued by the Autonomous Island of Anjouan, part of the Union of Comoros, rather than the UK Gambling Commission. This licensing arrangement places it in the offshore category: UK residents can register and deposit, but the operation sits outside the regulatory framework that governs locally licensed casinos.

The brand launched in 2024 and markets itself toward international players, emphasising cryptocurrency payment options, high-percentage welcome bonuses, and a game library focused on slots and live dealer tables. Several review domains use the Cactus Casino name, but they describe the same Ferzo-operated entity licensed in Anjouan. There is no evidence of multiple distinct operations trading under this brand, though promotional sites present varying bonus structures and regional messaging.

The absence of UK Gambling Commission authorisation is the defining regulatory fact. Ferzo Holding Limitada does not appear on the Commission's public register of remote gambling operators, and the Anjouan licence carries no formal recognition in Great Britain. This does not mean the site is illegal to access, but it does mean that UK consumer protections, dispute resolution mechanisms, and self-exclusion schemes do not apply.

What each identifying feature of Cactus Casino establishes

Characteristic	What it means for this operation	What it does not establish
Operator: Ferzo Holding Limitada, registered in Costa Rica	The corporate entity behind the site is identifiable and has a registered company number in Costa Rica. This provides a nominal legal identity for the operation.	Costa Rican registration does not confer gambling regulation or licensing. It establishes corporate existence, not authorisation to serve UK players or compliance with British consumer protection law.
Licence: Autonomous Island of Anjouan, Union of Comoros	The site holds a formal gambling licence from a recognised offshore jurisdiction. Anjouan licences are issued to international operators and impose basic operational standards.	An Anjouan licence is not recognised by the UK Gambling Commission. It does not grant UK regulatory standing, does not trigger UKGC dispute procedures, and does not make the site subject to British advertising or consumer protection rules.
Market positioning: high-percentage bonuses, cryptocurrency payments, international player base	The site targets players outside tightly regulated markets by offering larger promotional percentages and alternative payment methods that locally licensed casinos often restrict.	Marketing to UK players does not prove UK licensing. The presence of GBP currency options, British-themed promotional copy, or UK-accessible domains does not establish UKGC authorisation or local legal compliance.
Launch year: 2024	Cactus Casino is a recent entrant. The operation lacks the trading history that would allow assessment of payment reliability, dispute handling, or long-term game fairness over multiple years.	A recent launch does not imply illegitimacy, but it also does not provide evidence of established operational standards, sustained solvency, or a track record of resolving player complaints.

The brand name itself offers no regulatory information. "Cactus Casino" appears across multiple domains with similar visual design and identical operator details, suggesting a coordinated affiliate and mirror-site structure rather than competing businesses. The thematic branding and high-saturation welcome offers follow a pattern common among offshore platforms that position themselves as alternatives to UK-licensed sites, where bonus caps and stricter affordability checks apply.

Distinguishing offshore licensing from UK authorisation

An offshore licence permits a gambling business to operate legally within its issuing jurisdiction and often satisfies basic technical standards for software fairness and data handling. It does not, however, extend regulatory protection to players in other countries. The UK Gambling Commission requires any operator advertising to or accepting customers from Great Britain to hold a separate remote gambling licence issued under British law. Sites that lack this authorisation remain accessible but operate outside the scope of UK enforcement, complaint adjudication, and statutory protections.

When a casino holds only an Anjouan, Curaçao, or similar offshore licence, the practical consequences include the absence of GamStop self-exclusion integration, limited recourse through the UK's Alternative Dispute Resolution providers, and no guarantee that the operator will honour withdrawal requests or respond to complaints escalated to British authorities. Payment processors may also classify transactions differently, which can affect how banks and card issuers handle chargebacks or fraud claims.

The distinction is not between legitimate and illegitimate gambling but between regulated access within the UK framework and unregulated access outside it. A site may function reliably for some users while leaving others without formal recourse when disputes arise. The licensing jurisdiction determines which rules apply, not whether the platform technically works.

What remains unverified

Several material details about Cactus Casino cannot be confirmed from publicly accessible sources. The full ownership structure behind Ferzo Holding Limitada is not disclosed, and Costa Rican corporate registries do not always publish beneficial ownership. Game provision contracts—whether the site aggregates titles through a third-party platform or holds direct studio relationships—are not detailed in available documentation. Advertised return-to-player percentages, payout processing times, and the scope of responsible gambling tools remain operator claims rather than independently audited figures.

The Anjouan licensing authority does publish a register, but its transparency and enforcement mechanisms are not comparable to those of the UK Gambling Commission, Malta Gaming Authority, or other Tier-1 regulators. Confirming the active status of a Comoros licence typically requires direct inquiry or access to commercial compliance databases, which are not freely available to consumers.

These gaps do not prove misconduct, but they limit the due diligence a prospective player can perform independently. Offshore operations frequently offer less public disclosure than their UK-licensed counterparts, where regulatory reporting, complaint statistics, and financial stability assessments form part of the licensing regime.

Is Cactus Casino the same as Cactus Jack's in Nevada?

No. Cactus Jack's is a land-based gaming establishment in Carson City, Nevada, holding a nonrestricted licence from the Nevada Gaming Control Board. Cactus Casino is an unrelated online platform operated by Ferzo Holding Limitada and licensed in Anjouan. The shared cactus theme is coincidental; the two operations have no corporate or regulatory connection.

Does an offshore licence mean the site is illegal in the UK?

Not necessarily. UK law prohibits unlicensed operators from advertising to or actively targeting British consumers, but it does not criminalise individual play at offshore sites. The legal risk falls primarily on the operator. The practical risk for players is the absence of UK regulatory protections, including dispute resolution, self-exclusion, and financial safeguards that apply only to UKGC-licensed casinos.

Can I verify a casino's UK licence myself?

Yes. The UK Gambling Commission maintains a public register of all licensed operators at gamblingcommission.gov.uk. Search by company name or licence number. If the operator does not appear, it is not authorised to offer remote gambling to UK customers, regardless of what its marketing materials claim.

UK casino licensing and what it means for access

The UK Gambling Commission operates the licensing framework that governs all commercial gambling offered to consumers in Great Britain. Any operator accepting bets, wagers, or deposits from someone physically present in England, Scotland, or Wales must hold a remote operating licence issued by the Commission. This requirement applies regardless of where the company is registered, where its servers sit, or which other jurisdictions have issued it a licence.

A valid UKGC remote licence establishes several concrete protections. The operator must segregate customer funds from its own operating capital, meaning your balance sits in a separate account and remains protected if the company enters insolvency. Games must use certified random number generators, and return-to-player percentages must be audited and disclosed. The operator must integrate GamStop, the national self-exclusion scheme, and offer deposit limits, session reminders, and reality checks as standard tools. Complaints that cannot be resolved directly with the operator can be escalated to the Independent Betting Adjudication Service or another approved alternative dispute resolution provider, at no cost to the player.

Crucially, a UKGC licence also means the Commission can investigate, sanction, suspend, or revoke permission to operate. Enforcement actions range from formal warnings and financial penalties to licence withdrawal. The regulator publishes its decisions, creating a public record of compliance failures and remedial actions.

Offshore licences and their legal standing

An offshore casino is one that holds a licence from a jurisdiction other than the UK Gambling Commission and offers its services to British consumers without UKGC authorisation. Common issuing authorities include Curaçao, Malta, Gibraltar, Anjouan, and various other smaller jurisdictions. Each has its own regulatory standards, supervision intensity, and enforcement record.

Under section 33 of the Gambling Act 2005, it is an offence for an operator to provide facilities for gambling to persons in Great Britain without the appropriate licence. The offence sits with the operator, not the player: placing a bet at an unlicensed site is not itself a criminal act for the consumer. However, the practical consequence is that you play outside the regulated environment, and the protections described above do not apply.

A foreign licence does not confer permission to serve the UK market. A Malta Gaming Authority licence authorises remote gambling within Malta and toward jurisdictions that recognise MGA licences through mutual arrangements; it does not satisfy UK regulatory requirements. The same principle applies to licences from Curaçao, Anjouan, or any other offshore authority. Some offshore operators market their services toward British players despite lacking UKGC authorisation, relying on the fact that enforcement against foreign entities is complex and that players themselves face no penalty.

Distinguishing a UKGC-licensed operator from an offshore site

The most reliable method is to check the Gambling Commission's public register. Every licensed operator appears in the register with its legal entity name, trading names, licence number, and licence conditions. The register is searchable by company name or brand, and the entry will state whether the licence is current, suspended, or revoked.

A UKGC-licensed site must display its licence number and a link to the register in its footer or terms and conditions. The number follows a consistent format and can be verified directly against the Commission's database. If the footer shows a Curaçao, MGA, or Anjouan reference instead, the operator holds only that foreign licence and is not authorised under UK law.

GamStop integration is another clear marker. All UKGC-licensed operators must connect to the national self-exclusion scheme. If a site advertises itself as a non-GamStop casino or markets toward players who have self-excluded, it operates outside the UK framework by definition. This is sometimes framed as offering choice or freedom from restrictions, but the practical implication is that it holds no UKGC licence and the regulatory protections do not apply.

Payment methods can offer an indirect signal. UKGC-licensed operators work with UK banks and payment processors that conduct due diligence on the gambling licences they service. Offshore sites more frequently rely on cryptocurrency, e-wallets, or payment intermediaries that do not require UKGC authorisation. A reliance on crypto alone is not proof of offshore status, but it often accompanies it.

What changes when you play outside the UKGC framework

Fund segregation is not mandatory under most offshore licences. Your balance may sit in the operator's general account, and if the company becomes insolvent or simply stops processing withdrawals, you have no statutory protection and limited legal recourse. Complaint escalation to an independent adjudicator is not guaranteed; some offshore jurisdictions offer dispute resolution services, but they operate under different rules, timeframes, and enforcement powers.

Game fairness standards vary. Some offshore regulators require third-party testing of RNGs and publish RTP figures; others do not. Even where testing occurs, the frequency of audits, the transparency of results, and the regulator's capacity to enforce compliance differ significantly from the UKGC's requirements.

Self-exclusion tools depend entirely on the operator's own policies. GamStop does not apply, so a self-exclusion request made to one offshore site has no effect on any other. If the operator does not honour its own exclusion promise, your options are limited to whatever dispute mechanism the offshore licence provides, and you cannot escalate the matter to the UK Gambling Commission.

Advertising standards and bonus terms are governed by the offshore jurisdiction's rules. UKGC operators must meet specific standards for clarity, prohibited claims, and wagering conditions. Offshore sites may advertise higher bonuses, faster withdrawals, or better terms, but those claims are not subject to UK oversight. A 500% welcome bonus may come with conditions that make it impractical to withdraw winnings, and the promotional material is not required to meet UK transparency standards.

The distinction matters most when something goes wrong: a disputed withdrawal, a bonus that was not credited, a game result you believe was unfair, or an exclusion request that was ignored. A UKGC-licensed operator must respond to the Commission's inquiries, provide evidence, and comply with adjudication outcomes. An offshore operator answers only to its own licensing authority, and enforcement depends on that jurisdiction's willingness and capacity to act. In practice, resolution is slower, less transparent, and sometimes impossible.

Checking an unfamiliar casino brand

Verifying a casino's regulatory status requires checking the public register maintained by the authority named in its footer. For UK operations, the Gambling Commission publishes a searchable register at gamblingcommission.gov.uk that lists every licensed operator, the company holding each licence, and the activities each licence permits. The register updates in real time when a licence is issued, varied, suspended, or revoked.

An operator claiming UK authorisation must display its licence number in the footer of every page. That number can be entered directly into the Commission's register search. The result confirms the legal entity holding the licence, the brand names authorised under it, and whether the licence remains active. A site that omits the number, names a licence holder that does not appear in the register, or displays a number issued to a different operator cannot legally accept customers in Great Britain.

What an offshore licence actually establishes

Cactus Casino holds a licence issued by the Autonomous Island of Anjouan, part of the Union of Comoros. This jurisdiction does not impose the same fund segregation, dispute resolution, or responsible gambling requirements as the UK Gambling Commission. The central government of Comoros has described Anjouan licensing bodies as unauthorised entities operating outside its legal framework, and no bilateral recognition agreement exists between Anjouan and the United Kingdom.

An Anjouan licence permits the operator to host its platform and process transactions through service providers willing to work with that jurisdiction. It does not confer any legal standing in the UK, establish complaint rights under British consumer protection law, or require the operator to segregate customer funds. The licence itself confirms only that a registration process was completed and a fee paid to the issuing body.

Practical steps before registering

Check the footer for a company name and jurisdiction. A legitimate operator states exactly which legal entity holds the licence and provides either a licence number or a direct link to the regulator's verification page. If the footer names multiple jurisdictions or switches between them across different pages, that inconsistency warrants caution.

Search the named company independently. A corporate registry search in the stated jurisdiction should return a matching entity with a registration number and filing history. The absence of any corporate record, or a mismatch between the named entity and the domain's registered owner, indicates a structural problem.

Review the payment methods offered. UK-licensed operators work with established card acquirers and e-wallet providers that enforce their own compliance checks. A site that accepts only cryptocurrency, prepaid vouchers, or obscure payment processors may be avoiding the verification standards imposed by mainstream financial institutions.

Test the responsible gambling tools before depositing. UKGC-licensed sites must offer deposit limits that take effect immediately, self-exclusion that cannot be reversed during the chosen period, and reality checks that interrupt play at set intervals. An offshore site may describe these features without implementing them in a way that actually restricts access.

Understanding complaint and dispute routes

UK-licensed operators must subscribe to an approved alternative dispute resolution service and display its contact details prominently. If a player dispute cannot be resolved through the operator's own complaints procedure, the ADR service provides a binding or advisory determination at no cost to the consumer. Common ADR providers for UK gambling include eCOGRA, IBAS, and the Independent Betting Adjudication Service.

Offshore operators are not required to participate in any ADR scheme. Some display dispute resolution contact details, but these arrangements are voluntary and rarely produce enforceable outcomes for UK residents. The Gambling Commission has no jurisdiction over operators it has not licensed, so complaints about an offshore site must be directed to its own regulator—if one can be identified—or resolved through the operator's internal process.

Chargebacks through your bank or card issuer remain an option if the transaction was fraudulent or the service was not provided as described. However, many offshore operators structure their payment processing to make chargeback claims difficult, and success depends on the policies of the specific card network and acquiring bank involved.

Verification steps and their practical outcomes

Verification step	What it confirms	What it does not confirm	Consequence of a failed check
Search the Gambling Commission register using the licence number in the footer	The operator holds a current UK licence and the named company matches the register entry	Current game fairness, financial solvency, or customer service quality	The operator is not authorised to accept UK customers and offers no regulatory protections
Check for GAMSTOP integration and test a deposit limit	The site connects to the national self-exclusion scheme and enforces limits in real time	The operator will honour withdrawal requests or respond to complaints	Responsible gambling controls are either absent or not enforced, making self-exclusion ineffective
Look for an ADR provider logo and contact details in the footer	A dispute resolution route exists if the operator's own complaints process fails	The ADR determination will be enforceable or that the operator will comply voluntarily	No independent arbiter is available; disputes must be resolved directly with the operator or abandoned
Verify the legal entity in the stated jurisdiction's corporate register	A company with that name is registered and active in the claimed location	The company is solvent, that it operates the casino, or that customer funds are protected	The operator may be using a fictitious entity or a shell company with no operational substance
Review payment methods and processor names shown during deposit	The site works with recognised financial institutions subject to their own compliance standards	Withdrawals will be processed quickly or that your card details are stored securely	Payment processing may be routed through unregulated channels, increasing fraud risk and chargeback difficulty

No single check provides complete assurance, but the absence of a UK Gambling Commission licence removes the baseline protections that make other verification steps meaningful. A site that fails multiple checks—missing from the register, no ADR provider, cryptocurrency-only payments, no corporate record in the stated jurisdiction—presents compounded risk rather than isolated uncertainty.

Can I check whether Cactus Casino is licensed in the UK?

Cactus Casino does not hold a UK Gambling Commission licence. It operates under an Anjouan licence issued by a body in the Union of Comoros. You can confirm this by searching the Gambling Commission's public register at gamblingcommission.gov.uk; the operator and its parent company will not appear in the results.

What does it mean if a casino is not in the UKGC register?

An operator absent from the register is not authorised to offer gambling services to customers in Great Britain. It operates outside UK regulatory oversight, which means your deposits are not protected by fund segregation rules, you have no access to GAMSTOP or approved ADR services, and the Gambling Commission cannot investigate complaints or enforce standards.

Are offshore licences from places like Anjouan recognised in the UK?

No. The UK does not recognise offshore licences as substitutes for a Gambling Commission licence. An Anjouan licence permits the operator to host its platform in that jurisdiction but confers no legal authority to serve UK customers and does not establish any consumer protections under British law.

Risks associated with unlicensed or unverified casino sites

Operating outside the UK Gambling Commission framework removes the protections built into locally licensed casinos. An offshore site may accept your registration and deposit, but it does so without the legal obligations that accompany a UKGC remote licence. The absence of those obligations creates practical risks in fund security, dispute resolution, payment processing, and personal control over gambling activity.

Fund segregation and insolvency protection

UK-licensed operators must hold customer balances in segregated accounts, separate from the company's operating capital. If the operator enters administration or becomes insolvent, those funds remain protected and are returned to customers rather than distributed among general creditors. An offshore casino operating under a different jurisdiction's rules may not segregate funds at all, or may do so under a framework that offers no insolvency protection to UK customers. When such a site closes, whether through commercial failure, regulatory action in its home jurisdiction, or voluntary withdrawal, customer balances may become irrecoverable.

The risk is not theoretical. Offshore casinos have ceased operations with little notice, leaving customers unable to withdraw pending balances. Without a UK licence, there is no Commission requirement to publish financial audits, maintain minimum reserves, or provide advance notice before shutting down payment processing.

Complaint and dispute mechanisms

UK licence conditions require operators to offer an internal complaints procedure, respond within specified timeframes, and provide access to an approved alternative dispute resolution service if the complaint remains unresolved. These ADR providers issue binding decisions on the operator when a customer's complaint is upheld, covering matters such as voided winnings, incorrect bonus forfeitures, or account closures without explanation.

An offshore site may describe a complaints process in its terms, but it is not bound by UKGC licence conditions or overseen by the Commission's compliance team. If a dispute arises—such as a large withdrawal rejected on unclear grounds, or a bonus voided after wagering requirements were met—the operator controls both the internal review and the choice of any external adjudicator. Some offshore casinos nominate an ADR service, but without regulatory enforcement those decisions carry no binding weight. In practice, unresolved disputes with an unlicensed operator often end when the customer exhausts the available channels and the site declines further correspondence.

Payment processing and withdrawal reliability

Offshore casinos frequently rely on payment processors willing to handle transactions that UK banks and card networks classify as high-risk or prohibited. Deposits may process smoothly, but withdrawals introduce variables outside the operator's direct control. Payment providers can freeze accounts, impose additional verification, or withdraw service entirely, leaving customer funds in limbo while the casino seeks an alternative route.

Cryptocurrency withdrawal options, often promoted by offshore sites, shift the risk profile rather than eliminating it. Blockchain transactions are irreversible, so an incorrect wallet address or a processing error cannot be undone. Conversion rates between fiat deposits and crypto withdrawals fluctuate, and the operator determines the exchange rate applied. If the casino ceases operations or loses access to its wallet infrastructure, pending crypto withdrawals can become permanently inaccessible.

UK-licensed operators use payment providers authorised by the Financial Conduct Authority and are required to process withdrawals within a reasonable period. Persistent delays or unexplained withdrawal rejections at a UKGC-licensed site can be escalated to the Commission's enforcement team. No equivalent escalation path exists for offshore operators.

Self-exclusion and safer gambling tools

The UK licensing framework mandates participation in GAMSTOP, a national self-exclusion scheme that prevents excluded individuals from opening accounts or depositing at any participating operator. When you self-exclude through GAMSTOP, every UKGC-licensed casino must block your registration for the chosen period—six months, one year, or five years—and close any existing accounts. The scheme operates across all licensed brands, so exclusion from one operator extends to the entire regulated market.

Offshore casinos do not participate in GAMSTOP. An individual who has self-excluded from UK-licensed sites can still register, deposit, and play at an offshore operation without restriction. Some offshore sites offer their own self-exclusion tools, but these apply only within that single brand and rely on the operator's willingness to enforce them. There is no cross-industry exclusion, no independent oversight, and no mechanism to prevent the same customer opening a new account using a different email address.

Deposit limits, loss limits, and session reminders required at UK-licensed sites may be absent or optional at offshore casinos. When such tools exist, they are often presented as voluntary features rather than embedded controls, and the operator can modify or remove them without notice.

Game fairness and RTP verification

UK licence conditions require operators to ensure that all games meet minimum standards for randomness and return-to-player percentages. Slots and table games must be tested by accredited laboratories, and the operator must be able to demonstrate that live RTP matches the certified theoretical percentage. The Commission can request game data at any time, and persistent deviations from expected RTP can result in enforcement action.

An offshore site may publish RTP figures and display testing certificates from recognised laboratories, but without UK regulatory oversight there is no mechanism to verify that those figures reflect actual gameplay. The operator controls the game configuration, and changes to RTP settings or payout tables may occur without disclosure. Some offshore casinos source games from reputable providers whose own testing standards remain rigorous, but the absence of regulatory supervision removes the independent check that ensures continued compliance.

Marketing, bonus terms, and transparency

UKGC licence conditions impose strict requirements on advertising content, bonus disclosures, and the clarity of terms. Headline figures in marketing—such as welcome bonus amounts or free spin values—must be accompanied by the key conditions that apply, including wagering requirements, game restrictions, and expiry periods. Terms must be clear, unambiguous, and accessible before a customer commits funds.

Offshore operators are not bound by these standards. Bonus terms may be written in ways that obscure the practical conditions, such as maximum bet limits that void winnings if breached by a single spin, or contribution weightings that make meeting the wagering requirement impractical. Promotional material may emphasise headline bonus percentages without disclosing that the offer requires a deposit far above the minimum, or that most game categories are excluded entirely from bonus play.

When an offshore casino changes its terms, it does so without regulatory review. Customers may discover new conditions applied retroactively, or find that account balances are forfeited under clauses introduced after registration. The absence of a supervising authority means there is no independent review of whether terms are fair, transparent, or consistently enforced.

Data protection and privacy

UK-licensed operators handling personal data of UK residents must comply with the UK General Data Protection Regulation and the Data Protection Act 2018. This includes obligations to process data lawfully, store it securely, and provide customers with the right to access, correct, or delete their information. The Information Commissioner's Office enforces these requirements and can impose fines for breaches.

An offshore casino registered in a jurisdiction with weaker data protection laws may collect extensive personal information—identity documents, payment details, address history—without equivalent safeguards. That data may be stored on servers outside the UK, transferred to third parties for marketing purposes, or retained indefinitely even after account closure. If the operator suffers a data breach, there may be no obligation to notify affected customers or report the incident to a regulator.

Some offshore sites require additional verification steps, such as video calls or notarised documents, that go beyond the standard checks performed by UK-licensed operators. While presented as enhanced security, these measures place sensitive information in the hands of an entity with limited accountability and no oversight from UK authorities.

Legal and financial consequences

Playing at an offshore casino is not illegal for UK residents, but winnings from such sites exist in a regulatory grey area. While HMRC does not tax gambling winnings, financial institutions may scrutinise large deposits originating from unlicensed operators, particularly when those operators use payment processors flagged for money-laundering risk. Transactions may be delayed, frozen, or reported as suspicious activity, requiring the customer to provide detailed explanations and supporting documentation.

If a dispute escalates to the point where legal action is considered, pursuing a claim against an offshore operator presents jurisdictional challenges. The operator may be registered in a country with limited legal cooperation with the UK, and any judgment obtained in a UK court may be unenforceable abroad. Legal costs often exceed the disputed amount, making formal action impractical for most customers.

Can the UK Gambling Commission help with a complaint about an offshore casino?

No. The Commission regulates only operators holding a UK licence. If the casino operates under a licence from another jurisdiction, the Commission has no authority to investigate complaints, enforce terms, or compel the operator to take action. Your only recourse is through the operator's own complaints process or any dispute mechanism it chooses to recognise.

Are offshore casinos more likely to refuse large withdrawals?

The risk is higher. UK-licensed operators face regulatory consequences for unjustified withdrawal delays or refusals, including fines, licence reviews, and enforcement action. Offshore sites operate without that oversight, and some have been known to impose additional verification, invoke obscure terms, or delay payment indefinitely when faced with a large withdrawal. Not every offshore casino behaves this way, but the absence of external accountability removes the safeguard that protects customers at licensed sites.

Do offshore casinos report winnings to UK tax authorities?

Gambling winnings are not taxable in the UK, so there is no reporting obligation for the operator or the customer. However, if large sums are deposited into a UK bank account, the bank may ask for the source of funds as part of its anti-money-laundering procedures. The fact that winnings came from an offshore casino does not create a tax liability, but it may prompt additional scrutiny from your bank.