A British software engineer is suing the operator of crypto derivatives exchange BitMEX in London's Commercial Court, part of the High Court that handles major financial and commercial disputes, seeking the return of 324.8 BTC and alleging the platform traded with him without authorization from the UK's financial regulator.

The claim names HDR Global Trading, the company behind BitMEX, as defendant, according to The Guardian and particulars of claim reviewed by Decrypt. The Bitcoin at issue was valued at £20.4 million on October 1, according to the claim — about $27.2 million by Decrypt's calculation using the exchange rates cited in the filing.

The claimant, Lewis Barber, alleges BitMEX traded with him without authorization from the Financial Conduct Authority (FCA). His lawyers say other UK traders may have similar claims that could run to hundreds of millions of pounds in total.

Challenging 1,053 Losing Trades

Court documents show Barber opened around 2,294 trades on the exchange between 2018 and 2022 through five accounts. The claim targets the 1,053 trades that lost him money. All of them were perpetual swaps, a type of derivative similar to a futures contract but with no expiry date — a staple of crypto derivatives venues, typically traded with leverage that magnifies both gains and losses.

The filing argues that each trade constituted a regulated activity that BitMEX was not authorized to carry out in the UK, meaning none of them can be enforced against Barber under the Financial Services and Markets Act 2000. The Act makes agreements formed in breach of its authorization requirements unenforceable against the customer — the mechanism the claim relies on in seeking to unwind the losing trades and recover the stake.

According to the claim, BitMEX did not restrict access from the UK, allowed new users to select the country as their residence, and ran promotional campaigns worldwide, including an advertisement in The Times in January 2019. It also cites a March 2020 warning from the FCA that BitMEX may have been trading regulated investments in the UK without authorization. Customers who trade with unauthorized firms fall outside the protection of the Financial Services Compensation Scheme and the Financial Ombudsman Service, the standard recourse channels for UK investors.

Barber is additionally seeking damages for deceit, alleging BitMEX knew it was not authorized when it implicitly represented that it could lawfully trade with him. His solicitors wrote to BitMEX in December 2025 rescinding the trades, according to the claim.

The claim has been filed but not yet formally served on BitMEX, the Guardian reported. "No such claim has been served on HDR Global Trading Limited," a BitMEX spokesperson told the newspaper. Formal service would be the next procedural step, after which the exchange would have the opportunity to respond to the allegations in court.

A Troubled Legal History

BitMEX separately faces a proposed class action in New York alleging theft of Bitcoin and insider trading, which names co-founders Ben Delo, Arthur Hayes, and Samuel Reed. The three pleaded guilty in 2022 to violating the Bank Secrecy Act through anti-money laundering failures at the exchange and were pardoned by President Donald Trump in March 2025. BitMEX itself pleaded guilty to Bank Secrecy Act violations in 2024 and was ordered to pay $100 million in January 2025.

BitMEX in the UK

BitMEX shut down on September 23, having announced its closure in July. In September, Delo gave £36 million to Reform UK, the largest single donation in British political history, as Decrypt reported.

Barber's law firm, Seladore Legal, said in a statement shared with Decrypt that many other investors are likely to be in a similar position, putting the potential total at hundreds of millions of pounds.

"Other UK-based persons may have entered into similar contracts with BitMEX, although whether any individual has a claim will depend on the particular facts and trading history," said Gareth Keillor, a partner at the firm.