In brief

• UK software engineer Lewis Barber is suing the operator of BitMEX, the crypto derivatives exchange that shut down in September, in London's Commercial Court.
• Barber wants 324.8 BTC returned, alleging BitMEX traded with him without authorization from the Financial Conduct Authority, the UK's financial regulator.
• His lawyers say other UK traders may have similar claims, which could run to hundreds of millions of pounds in total.

A British software engineer is suing the operator of crypto derivatives exchange BitMEX for the return of 324.8 BTC, alleging it traded with him in the UK without regulatory approval, according to The Guardian and particulars of claim reviewed by Decrypt.

The Bitcoin was worth £20.4 million on October 1, the claim says, or about $27.2 million by Decrypt's calculation using the claim's exchange rates.

Lewis Barber, who brought the claim against BitMEX operator HDR Global Trading, entered into around 2,294 trades on the exchange between 2018 and 2022 from five accounts, the claim says. It challenges the 1,053 that lost him money.

All of them were perpetual swaps, a derivative similar to a futures contract but with no expiry date. Each trade was a regulated activity that BitMEX was not authorized to carry out in the UK, the claim argues, so none can be enforced against Barber under the Financial Services and Markets Act 2000.

The claim says BitMEX did not restrict access from the UK, let new users select it as their country of 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.

Barber also claims 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 rescinding the trades in December 2025, the claim says.

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.

BitMEX also 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 co-founders 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 in July that it would close.

Delo gave Reform UK £36 million in September, the largest single donation in British political history, Decrypt reported.

Many other investors are likely to be in a similar position to Barber, his law firm Seladore Legal said in a statement shared with Decrypt, 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.