I remember my parents watching the Alec Guinness version on tv in the late seventies, not very long after the period in which it was set, 1973.
This version is then very much a period piece, London still looking and holding onto its postwar grubbiness which lasted until the early eighties, the predominant colors in this film are grey, brown and misery - like its characters. But it is worth watching. Spying isn't remotely glamourous but tedious and boring and nasty and all the cheap thrills associated with knowing other people's secrets are here.
There is one great scene where an ex-agent, now a school teacher, says to a fat, bespectacled, lonely and bullied boy 'You notice things, lonely people like us are good at watching', and loneliness is everywhere - washed down as usual with big glasses of alcohol, mistrust of friends, mistrust of enemies, mistrust of entire countries and so it goes on. The despairing lesson here is 'Don't trust anyone'.
You yearn for a politician from either side to have the nerve to say 'some of your ideas are good and some of ours are bad, can't we take the best from each other and scrap the bad ones', but instead it's the usual we're right and you're wrong. Today it is ten years exactly after 9/11 and it might as well be the day after.