Here is John Barry's superb and oh-so-evocative theme to The IPCRESS File, IPCRESS standing for 'Induction of Psycho-neuroses by Conditioned Reflex under strESS'.
It was powerful stuff, very well written by Len Deighton in the original novel (in which the lead character, speaking in the first person, never disclosed his name, so a name had to be devised for the movies) and capturing so much of the real-world atmosphere of how the spying business must have operated.
The story had its moments of humour, and the movie in particular had some top-notch performances from our stock of dependable British actors, from Michael Caine as 'Harry Palmer', via Guy Doleman as Colonel Ross, to Nigel Green as Major "now listen to me!" who turned out to be batting for another side.
As the antidote to the glamour and over-the-top wizardry of the James Bond franchise, it was much more gripping stuff and much more close-up somehow. The IPCRESS theme is particularly closed-in claustrophic and completely haunting. Indeed, it was one of the earliest pieces for which I almost immediately memorised the entire orchestral arrangement (something of which I do a lot, by the way)...