If there is such a thing as the epitome of British Comedy it is probably Monty Python, their highly lauded TV show Monty Python's Flying Circus and their films:
The show from which the group takes its name is not where it all started: At Last The 1948 Show, Do Not Adjust Your Set, and How To Irritate People can all be cited as direct precursors inasmuch as all the elements that were later to comprise Monty Python's Flying Circus were there already, even to the extent that material of these programmes was reused. The style is indebted to Spike Milligan, Peter Cook, Dudley Moore and of course Marty Feldman (Marty, At Last The 1948 Show) with whom they had collaborated before. But the show itself was where it all gelled, where comedy, sketches and slapstick were taken to a new level insofar as their humor not only satirized cultural institutions, but became one in its own right.
The Liberty Bell March by John Philip Sousa, which was used because it was in the public domain, can never again be played in earnest as a military march. Asteroids have been named for the group and its members. Guido van Rossum took the name for his programming language from the group and called the development environment IDLE. The word "spam" for unsolicited email has been derived from a sketch in the programme. And their ridiculing of philosophy has itself become the subject of philosophy lectures, scholarly articles and textbooks.
Describing their style (which is of course pythonesque and has become a word of the English lexicon) is probably as superfluous as giving a summary of their sketches as they have circulated the internet from usenet groups to Wikipedia to countless fan sites to email signature blocks to online video services and so on and so forth. If you really have not heard of them, you might as well not have lived and you should immediately rectify this by doing a quick search using your favourite search engine.
And now for something completely different …