British tech magnate Mike Lynch has appeared in court in the US to rebut claims that he committed fraud to inflate the value of his company ahead of its sale to Hewlett-Packard in 2011.

He told the jury that he was uninvolved with the transactions that had been described in the trial, reportedly describing watching the proceedings as “surreal”.

Mr Lynch co-founded the software firm Autonomy in 1996, which grew to be one of the UK’s biggest companies.

An entrepreneur who once drew comparisons to Bill Gates and Steve Jobs, he now faces up to 25 years in prison if convicted.

Prosecutors in San Francisco have spent weeks questioning witnesses, aiming to convince the jury of their case.

They claim that Mr Lynch was the “driving force” behind a scheme, using back-dated contracts and other manoeuvres to inflate the value of the firm, which ultimately sold for more than $11bn (£8.6bn).

At the time, the deal ranked as the largest-ever takeover of a British technology business.

Just a year later, HP wrote down the value of Autonomy by $8.8bn.

HP claimed it had been duped into overpaying for the company, which was known for software that could extract useful information from “unstructured” sources such as phone calls, emails or video.

Mr Lynch’s team has argued that HP did not properly vet the deal.

It has also worked to distance Mr Lynch from other executives, including its former chief financial office, who was already successfully prosecuted for fraud.

Under questioning from his lawyer on Thursday, Mr Lynch said his focus at the firm was technology and marketing and he left others in charge of the numbers.

He made the case that business was complex, saying: “If you take a microscope to a spotless kitchen you’ll find bacteria.”

Mr Lynch, a former UK government adviser who sat on the boards of the BBC and the British Library, vigorously fought attempts to bring him to trial in the US.

He was eventually extradited after a UK judge ruled in favour of HP in a similar civil fraud case in 2022. HP is seeking a reported $4bn in that case.

As well as Mr Lynch, Autonomy’s former finance executive Stephen Chamberlain is also on trial.