To his family and friends in Derbyshire’s Amber Vale, Bryn Jones was a devout churchgoer and devoted family man with a respected career in the aeronautics industry.

But on Thursday they woke to news that the cheerful and polite man who made a point of greeting his neighbours every day had been arrested under the Official Secrets Act, on suspicion of spying for the Chinese.

Mr Jones, the former chief combustion technologist at Rolls-Royce’s aeronautical division in Derby, was arrested at his home on Tuesday by officers from Scotland Yard’s SO15 counter-terrorism command.

Police moved in after MI5 reportedly received information that classified details about the RAF’s new £100 million F-35 Lightning II jet – key parts of which were made by Rolls-Royce – had been passed to Beijing.

A search warrant was also executed at an office in the West Midlands linked to the father-of-five.