I was going to list all the UK sitcoms that have "jumped the shark" but then i realised that i cannot think of any! well, with the possible exception of all the dressing up on Are You Being Served, although you could argue that it was part of the show. In general, i think, most British sitcoms die off before they get silly

(If you don't know what jumping the shark is, its when a TV programme goes a bit too far in bringing in new ideas to a show, normally in desperation like adding long lost family members or really silly and out of character situations, normally marking the start of the death of a show as viewers stop watching, sniffing the desperation! . The name comes from a moment in the US 'com "Happy Days" where Fonzy literally jumped a shark while waterskiing. Johnny in "Two Pints" dies while jumping a shark which was a joke on the part of the show's writers)

List your "Jumping the Shark" moments

Yes Rogue, the two that spring to my mind are "Are You Being Served" and "Two Pints".

AYBS started off great in my opinion but by the end it was just ridiculous - especially when Mr. Humphries gets with Miss Brahms in the last episode.  

I always liked Two Point 4 Children and while I maintain that over the 8 series there was never a 'bad' episode, the later ones became more and more formulaeic  and lost the mysterious darker side that series 1 and 2 have.  I think if it had continued the only way forward was to jump the shark, it came very close and I'm glad that one ended when it did (although it ended because of Gary Olsen's untimely death which was a great shame).

As a huge Steptoe fan I think Steptoe jumped the shark in the episode "The Seven Steptorai", one of the least watched in this household, perhaps because the production quality of the end fight scene is so terrible, but the make up on the younger actors to make them look old was terrible and the fight scene is just far fetched.  However, I still can't bring myself to call it a bad episode as I could nevr say that!! lol

Possibly not a Jumping the shark moment, but a totally out of character moment that I always remember is in Only Fools and Horses in the episode 'To Hull and Back'.  Del knows Boycie paid the diamond dealer in forged tenners.  When he sees the pile of money Boycie paid him with at the end, he thinks they are fake and throws them out of the window.  I am disappointed that John SUllivan made such a glaring error - 1, Del Boy could tell the difference between a real and a fake just by looking at it - as established earlier - but also as a market trader he would tell in an instant.  2, If Del had been paid in dodgy tenners, he would have tried to pass them off to someone else.  The ending ruins what I think is a good episode.  

yeah, i agree wit you on all three programmes you mentioned, although i vaiguely remember the AYBS episode, i cannot remember the details. 2 Point 4 Children was rather dark in its early days wasn't it? With that biker and all. And yeah, the ending of To Hull and Back was very weak even though the programme had some funny bits like when the threesome thought that the police were chasing them in Amsterdam.