Asked in The Guardian's Notes & Queries:
I notice Channel 4 is again screening the Christmassy Ted episode of Father Ted. Which episode of a TV series (as opposed to one-offs such as The Snowman) has been screened most often on one of the five main TV channels?
The five main TV channels are the UK's BBC1, BBC2, ITV, Channel 4 and Channel 5. The answer doesn't necessarily need to be a Christmas special. I'm looking for some concrete basis to the answer rather than guesswork.