LONDON (Reuters) - Mike Lynch, the tech tycoon missing after his luxury yacht sank off Sicily, spent more than a decade building Britain's biggest software company and then almost as long again fighting fraud charges related to its multi-billion pound sale.

Lynch founded Autonomy from his ground-breaking research at Cambridge University in 1996, and was lauded by shareholders, scientists and politicians when he sold it to Hewlett-Packard for $11 billion 15 years later.

But in late 2012, HP stunned Wall Street and the City of London by alleging a massive accounting scandal at the business, and writing off $8.8 billion of its value.

Lynch, known for an abrasive intellectual charm, said HP did not know what it was doing with Autonomy, which searched and organised data using patented algorithms based on a mathematics developed in the 18th Century by Reverend Thomas Bayes.

He spent the next 12 years in courts trying to clear his name, locked in some of the biggest legal battles in corporate history.

HP pursued Lynch in London's High Court for $5 billion. It won most of its case in 2022 and is still awaiting the award of damages.

The judge found that Lynch and another colleague had fraudulently concealed a "fire sale" of hardware and engaged in convoluted reselling schemes to mask a shortfall in sales of Autonomy's software, the business HP coveted.

U.S. authorities filed criminal charges including wire fraud and conspiracy against Lynch and sought his extradition.

The British government came under pressure from Lynch's supporters to block the application. If found guilty, Lynch could have faced decades in jail.

But the appeals failed, and Lynch took the stand in San Francisco in his own defence, where he denied wrongdoing and told jurors that HP had botched the integration of Autonomy.

He was acquitted on all charges and freed after a year under house arrest. Lynch said he was "elated".

"I am looking forward to returning to the UK and getting back to what I love most: my family and innovating in my field," he said.

VIOLENT STORM

A person familiar with the rescue effort said Lynch and his wife, Angela Bacares, were on the 56-metre (184-ft) long British-registered Bayesian sailboat when it was struck by an unexpectedly violent storm and sank off the Sicilian capital Palermo early on Monday.

The yacht was owned by Lynch's family and had 22 people on board when it sank just before sunrise.

Lynch was born in 1965 and was raised in Chelmsford near London where his mother was a nurse and his father a fireman. He said his parents instilled in him an appreciation of the value of education.

At Cambridge University, he studied physics, mathematics and biochemistry, and went on to research signal processing for his doctorate. His thesis is still one of the most widely consulted in the university's library, reports have said.

In 1996, Lynch founded Autonomy which searched and organised complex data such as emails, phones calls and video.

Lynch, who has a herd of rare breed cattle on his estate in Suffolk, East England, used some of the proceeds of the sale of Autonomy to set up venture capital firm Invoke.

It was a major backer of Darktrace, a British cyber security company that U.S. firm Thoma Bravo agreed to buy for $5.32 billion in cash in April.

(This story has been refiled to correct picture caption)