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.