It seems extraordinary that a book as famous as Len Deighton’s The IPCRESS File has only been adapted once, but when the film is as iconic as the 1965 Michael Caine vehicle, it’s not that inexplicable. Nearly sixty years on, Sidney Furie’s picture is less distinctive for its storyline than for its aesthetic, exemplified by Caine’s thick-rimmed dark glasses, John Barry’s much-sampled score and Otto Heller’s cinematography, all of which make it a British example of the then-modish cinema du look genre. Two sequels followed, both based on Deighton novels, but the original’s standing as one of the definitive spy pictures has never been challenged. Until now, anyway.

It would be more unusual in a show like this if the privately educated won

Purists will carp. (Purists always carp. That’s why they’re called purists.) But the new ITV series based on the novel is a generally enjoyable mixture of homage and reinvention. Yes, Joe Cole’s Harry Palmer, a morally dubious former British Army sergeant who is recruited to help MI5 find a missing nuclear scientist, is clearly styled to look and act in a fairly similar fashion to Caine, even down to the dark glasses, and if Tom Hodge’s score made any more obvious nods to Barry and 60s spy music generally, it would find itself going for “a quiet chat” along the Embankment with a shady figure called Nigel. James Watkins’ direction has so much love for the tilted Dutch camera angle in scenes, that one begins to wonder if one’s screen is on the blink. Still this is a worthwhile revisit that should ensure that Sunday evening espionage drama remains a constant in many households.

Its single most successful element so far is the casting of the great Tom Hollander in the role of Dalby, the cynical spymaster — is there any other kind? — who springs Palmer from a military prison to aid him with his quest. It seems strange to remember that when Hollander began his career, directors often seemed uncertain what to do with him, casting him either in pretty-boy roles or as undistinguished villains. As he advances louchely into middle age, his once-choirboyish looks now rumpled and seedier, it is hard not to be reminded of the great Denholm Elliott, an actor so associated with scene-stealing that Gabriel Byrne once ruefully said of him, “Never work with animals, children or Denholm Elliott.” Hollander has now become much the same kind of actor; his presence in anything buoys it immensely. I am glad that he is in work, because otherwise I fear for his afternoon activities.

The key dynamic between Hollander’s Dalby and Cole’s Palmer is based around class. Dalby is, superficially at least, an old-fashioned public-school type, “the man from the Ministry”, who wears immaculate three-piece suits and takes Palmer for lunch at his club. Palmer, meanwhile, speaks with a working-class accent, and responds with icy contempt to Dalby’s sneering belittlement of his humble background. The class dynamic between the two of them is well observed, especially the strong hints that Dalby will turn out to be rather more complex than he initially appears, and no doubt the chippiness that Palmer displays will soon be vindicated. It would be more unusual in a show like this if the privately educated won.

This is very different to the James Bond novels that Deighton’s series was intended as a corrective towards. Ian Fleming created his superspy character in his own image as a louche, hedonistic sort, much given to womanising and gambling and drinking. Both character and author’s Old Etonian backgrounds are deployed as a kind of cloak of honour, ever-ready to serve Queen and country. Deighton and Palmer, meanwhile, also had a great deal in common, although it was less a background of Bollinger and caviar and more beer and boiled eggs.

Sometimes one’s reasons are more complicated than a lack of inspiration

The author began his career in advertising in the 50s, where he found himself working alongside untalented but arrogant public schoolboys who brought their own unique brand of well-spoken vacuousness to the job. He stuck it out as long as he could, and then pivoted to writing and illustrating cookery columns for The Observer, even as he attempted to get his novel published. Although nominally a spy thriller, it was as much part of the Angry Young Man genre of class consciousness as the likes of Room at the Top and Saturday Night and Sunday Morning, albeit with more shooting and nuclear intrigue. Deighton explicitly said, “The IPCRESS File is about spies on the surface, but it’s also really about a grammar school boy among public school boys and the difficulties he faces.” Like many writers, he chose to use espionage as a metaphor, on this occasion for failing to fit into an exclusive and snobbish milieu. It became an instant bestseller and guaranteed him entry to the highest echelons of the club, nominally at least.

Deighton is still alive, at the age of 93. He has consistently kept a low public profile, eschewing interviews, literary festivals and the general rum-tum-tuggery of the publishing industry in favour of a much quieter life; he has not published a novel since 1996, while his contemporary John le Carré has been so prolific that books have continued to be released under his name posthumously. Yet le Carré (Sherborne, Oxford) is one of the “posh boys” (despite a rather chequered background and rackety father) who Deighton has always seen as his foes, and who, inevitably enough, make up much of the strata of the British literary industry.

In a line that could have been uttered by Palmer, Deighton once said, “The best thing about writing books is being at a party and telling some pretty girl you write books, the worst thing is sitting at a typewriter and actually writing the book.” He has also called the endeavour “a mug’s game” and has candidly said that he doesn’t miss it at all. For someone as accomplished and witty as Deighton, it seems a shame that there are not more of his excellent stories to enjoy. Yet, as The IPCRESS File so elegantly demonstrates, sometimes one’s reasons to write, or not write, are more complicated than a simple lack of inspiration.

As the nation watches this latest tale of espionage — only partially coloured by real-life events taking place in Russia, and beyond — it is hard not to remember, in its themes of class antagonism and betrayal, that its creator had a very specific purpose in mind, and that once a wrong ‘un, always a wrong ‘un. This simple but essential edict remains something that our very own Prime Minister (Eton, Balliol) might be minded to realise in his current woes.