A man in his 70s has been arrested as part of a probe under the Official Secrets Act, police said on Thursday, amid reports he was a former Rolls-Royce engineer suspected of divulging secrets about Britain’s new stealth fighter to China.Scotland Yard said the man was arrested on Tuesday afternoon and taken to a police station in Derbyshire before being released under investigation.A search at an address in Derbyshire was ongoing while a search warrant was also executed at an office address in the West Midlands.The man was named by the Sun as Bryn Jones, a former chief combustion technologist, who it said had been detained in connection with efforts by China to obtain classified information about Britain’s new £100million RAF stealth fighter jet.The 73-year-old former Rolls-Royce employee was reportedly held after MI5 received information that classified details were passed to Beijing. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. The F-35 programme is the world’s largest defence development, worth over $1.3trillion. UK industry provides 15 per cent of each of the 3,000 aircraft currently on the order books and at peak production 25,000 British jobs will be supported throughout the supply chain. He was detained in an “ultra-discreet” swoop by officers from Scotland Yard’s SO15 counter-terrorism command at his home on Tuesday, it was reported.Mr Jones, who describes himself as a “visiting professor” in “gas turbine combustion” at the Aeronautical University of Xian, central China, denies any wrongdoing, the newspaper reported. The investigation reportedly centres on information about the F-35 Lightning II jet, which arrived in Britain last week. Britain has committed to buying 138 F-35 fighter aircraft and has so far bought 48 at a cost of £9.1 billion.