We love Fawlty Towers, and can quote most lines from them, and Brideshead Revisited was darn good, but the best series ever made for TV was from John LeCarre's book Tinker, Tailor, Soldier, Spy. Six hours of dark, haunting intrigue, with the best casting imaginable. Alec Guiness is understatedly great, of course, but the others are equally remarkable. The character development is the best part of the series: the spy stuff provides the dramatic tension.
Even in the post cold-war era, one hell of a story. Perfect TV. See it.