When Richard Burton became a superstar, he insisted on casting his friends from his days at the Old Vic and West End (London's equivalent of Broadway). That is why Claire Bloom, who is clearly too old to be a teenager, was cast as Nan Perry. Other friends of Burton's cast in the film included the great stage actor Sir Michael Hordern and Robert Hardy.
Author John le Carré worked for British Intelligence MI5 and MI6 during the 1950s and 1960s and worked in Berlin where this film is partially set. Le Carré was there when the Berlin Wall was being constructed. Le Carré drew on this real life experience when he wrote the novel of 'The Spy Who Came in from the Cold'. The novel is set about a year after the Berlin Wall was built.
John le Carré included 'The Spy Who Came in from the Cold' as one of his 4 best novels during an interview on 5 October 2008, on BBC Four. The other best works he selected were; 'The Tailor of Panama', 'The Constant Gardener' and 'Tinker, Tailor, Soldier, Spy'.
The name of the character of Liz Gold from 'The Spy Who Came in from the Cold' novel was changed to Nan Perry (played by Claire Bloom) for this film. It is considered that the reason for this was because lead actor Richard Burton was married to actress Elizabeth Taylor at the time, and changing the character's name prevented any possible name-jibes that could be vented from the media.
In a 2016 article for The Guardian, John le Carré revealed fond memories of the shoot: 'The director and I got along fine. I enjoyed an amiable relationship with the screenwriter [Paul Dehn], who as a former instructor in the black arts at a British spy school during the second world war, turned out to know much more about espionage than I did. No great liberties were taken with my story - although I no longer see that as a criterion - and my only job was to provide the odd grace note to the screenplay while befriending Richard Burton and keeping a beady eye on his alcohol consumption.' Although he recalled 'open hostility' between Burton and director Martin Ritt, he believed this 'fed Burton's sense of alienation, and gave force to his performance.'
The character of Hans-Dieter Mundt (played by Peter van Eyck in this film) was changed to Karel Harek aka 'Blondie' for John le Carré's The Deadly Affair (1966), because Paramount Pictures held the rights to the character's name from this film.
Richard Burton and co-star Warren Mitchell were Royal Air Force cadets together at Oxford in 1944, where they knew one another and became friends. From 1944-47, when both were demobilized, they were stationed together at times in Canada and back in England.
The character of George Smiley, John le Carré's iconic character, was renamed Charles Dobbs for John le Carré's The Deadly Affair (1966) because Paramount Pictures had bought the film rights to the 'Smiley' name when they produced this film.
John le Carré said in an interview with The Guardian 13th April 2013: "I wrote 'The Spy Who Came in from the Cold' at the age of 30 under intense, unshared, personal stress, and in extreme privacy. As an intelligence officer in the guise of a junior diplomat at the British Embassy in Bonn, I was a secret to my colleagues, and much of the time to myself. I had written a couple of earlier novels, necessarily under a pseudonym, and my employing service had approved them before publication. After lengthy soul-searching, they had also approved 'The Spy Who Came in from the Cold'. To this day, I don't know what I would have done if they hadn't."
In the Criterion remastering of the film, is Included an interview with 'John le Carre', in which he expressed his wish for Rita Tushingham to have portray Nan Perry, as he felt she'd be 'a bit kooky, someone who could play working class, a bit solitary... a natural recruit for the communist party.' Initially le Carré felt 'Claire Bloom' 'too beautiful, classy' for the role. Far from being disappointed with her performance in the film, le Carré said 'she provided the female-focus the story needed, and (she) radiates tremendous confidence...she knew she wasn't going to be acted off the screen (by 'Richard Burton').'
Writer John le Carré partially based his famous George Smiley character on a friend, the Lincoln College tutor and Oxford University don, the Reverend Vivian Green. Smiley was also based on le Carré's boss at MI5, Lord Clanmorris, who wrote crime novels under the pseudonym of John Bingham.
This film's title was spoofed in Le spie vengono dal semifreddo (Dr. Goldfoot and the Girl Bombs (1966)) which translates literally into English as "The Spies who came in from the Semi-Cold". or more idiomatically "The Spies who came in from the Frozen Custard".
First of two screen adaptations of a John le Carré story scripted by Paul Dehn. The second would be The Deadly Affair (1966) released in the next year. Just before this movie, Dehn also co-wrote the script for the James Bond movie Goldfinger (1964).
According to Wikipedia, in 2005, the 50th anniversary of the Dagger Awards, John le Carré's. novel, The Spy Who Came in From The Cold, was awarded the 'Dagger of Daggers'; a one-time award given to the Golden Dagger winner regarded as the stand-out amongst all 50, previous winners throuhout the history of the Crime Writers' Association.
The 50th anniversary of John le Carré's novel, was celebrated in 2013, with a new edition of the book, published by Penguin Books on 1st August of that year. The boook includes a "Fifty Years Later" introduction by John le Carré.
John le Carré's novel is included in TIME magazine's list of All Time 100 Novels, in which the book's ranked at N°. 88 spot where critics Richard Lacayo & Lev Grossman selected their 100 Best English language novels published since the beginning of TIME in 1923.