Somehow, I have managed to remain completely oblivious to the BBC4 game show Only Connect until very recently.
Axel first brought it to my attention in this comment, but this week Jeremy showed me the Only Connect flash game. This is based on the third round in the programme. You're given sixteen words, and you have to spot the connections and put them in four groups of four. Your task is hampered by the subtlety and obscurity of some of the connections and further hindered by the tendency for some words to fall into more than one category. The red herrings don't make it any easier. The grid is, however, crafted such that there is only one solution.
Having tried the flash game with limited success, and with the words "No, that's not a group" ringing repeatedly in my head, I then watched all the previous episodes in the current series, helpfully retained by the BBC's iPlayer for people like me who get addicted to it after one episode and spend the weekend yelping answers at the screen.
It's what you might expect if you combine "BBC4" with "game show". The questions range from merely difficult to effectively impossible, hardly anyone has heard of it, and there aren't any prizes. It's further evidence of the law of game show difficulty; in general, the lower the value of the prize given to the eventual winner, the higher the quality and difficulty the game show. Classic game shows such as Mastermind, University Challenge, Countdown and Fifteen to One don't/didn't need to give away huge prizes, as the possibility of becoming the champion of such a competition is enough incentive for the contestants1. Only Connect is in the same category as these shows, except that its position on BBC4 ensures that most people won't even know about it.
That's not to say it should necessarily move from there, though. If it were transferred to a more mainstream channel, the BBC might be tempted to effect some ill-advised tinkering with the format in fear of the Daily Mail headline "licence fee spent on baffling your children with impossible quiz", so perhaps BBC4 is its natural habitat.