In 1964, a 31-year-old Michael Caine was having dinner with his roommate Terence Stamp at the Pickwick Club in Soho, when the big-cheese producer Harry Saltzman sent a note over to their table, asking Caine if he’d like to chat over coffee afterwards.

Caine had been toiling in films for 15 years with little reward, and while he’d just shot his best role to date in Zulu (1964), the £4,000 salary wasn’t likely to keep him in filet mignon for long – certainly not compared with his friend Sean Connery, who’d just earned an enviable £500,000 for the third James Bond film, Goldfinger.

Saltzman was co-producer on the Bonds with Cubby Broccoli, and Caine immediately assumed he might be in line for a small part. But the proposition, instead, was a career-changer. Saltzman asked him if he was familiar with Len Deighton’s 1962 novel The Ipcress File, which, as it happened, Caine was right in the middle of reading.

Saltzman had just snapped up the rights for £12,500, and had been looking in vain for his leading man; even though the nameless main character, a nondescript spy, was worlds apart from the posh officer Caine had just played, the producer saw star quality. And he wasn’t wrong. On the spot, he offered Caine a seven-year deal, which the cash-strapped actor delightedly accepted. One thing: his real accent would be much more suitable this time than the Zulu one.

This murky tale of Cold War brainwashing, almost 60 years later, is becoming a new TV mini-series, airing on ITV in the spring. Back then, Saltzman earmarked The Ipcress File as “Bond on a budget”, but Caine and everyone else who worked on the original film had other ideas. First they needed a name – “Harry Palmer” was Caine’s idea – to make the spy sound as ordinary as possible. They wanted him to be a kind of anti-Bond: deglamorised, insolent, and glumly going about his job in mid-1960s London, while living in a Notting Hill bedsit. He even wore glasses, which practically no male lead since Harold Lloyd had done.