Jonathan Creek BBC1, 9pm The Krypton Factor STV, 7.30pm Thatcher and the Scots BBC2, 9pm There was a good line in Jonathan Creek . However, as Alan Davies delivered it in the same tone as the bad lines, it was easy to miss. Creek had been called to a gothic mansion owned by a magician, to investigate the disappearance of a woman who had foolishly decided to sleep in the haunted attic, even though all the previous guests had disappeared. In the morning, all that remained was a ripped pair of tights, so her friend - a sassy blonde played by Sheridan Smith in a rah-rah skirt - called for Creek. "This is Joey Ross," said the magician's mother. "Yes," said Creek, "I always loved you as Ritzik in Sergeant Bilko." (Joe E Ross played Ritzik in the Phil Silvers Show).

Alan Davies would have known that, even if Jonathan Creek wouldn't, but it really is difficult to tell the difference between the comedian and the accidental detective in David Renwick's comedy drama. Davies doesn't act, he tries to stay awake, occasionally pausing for a cryptic insight. "Ectoplasm everywhere," he will say, "but how?" Or, asked by his blonde assistant why he is staring at a ladder, he will murmur: "You're staring at a ladder. I'm staring at a hypotenuse." (It is oddly reassuring to hear the word "hypotenuse" on popular television.) While others were getting excited about the ectoplasm, he remained level-headed, despite his curly perm. "I think we know what hasn't happened," he said. "We know she wasn't abducted by an evil spirit and whisked away to the other side."

Several hours later, the mystery was solved. Creek's knowledge of right-angled triangles, plus a schoolboy fluency in Latin, led him to deduce that the murders were committed by a malevolent bathtub; a plan so cunning that Joey forgot to grieve for her murdered friend.

Allan Little didn't uncover any ectoplasm in his thoughtful documentary, Thatcher and The Scots , but there were ghosts, some scarier than others. Baroness T was absent, but was represented on earth by her Scottish Baldricks, Messrs Rifkind and Lang, who tried to defend their former boss without actually stating that she was right. Sir Malcolm Rifkind did attempt to absolve the Iron Lady for the early introduction of the poll tax (it was George Younger's idea), while Baron Lang of Monkton lost himself in a mist of mixed metaphor. Thatcher, apparently, "was clearing away the debris of what was already a desert on a life-support machine, and the life support machine was one of taxation pumped in by the Westminster government". It's good that we got that cleared up, but Little's more radical idea - that Thatcher gave birth to our confident, devolved nation, yet received no thanks - was resisted by most of his interviewees. Tommy Brennan, a former Ravenscraig shop steward, gave her some credit. She brought the salmon back to the Clyde, he said. By destroying Scottish industry.

In the mysteriously-revived Krypton Factor , David, an investment banker from London, beat Gordon, a customer services manager from Aberdeen, Naomi, a management consultant from Kent, and Jonathan, a student at Cambridge University. This may make him the only successful investment banker in Britain, though the Krypton Factor posed an unusual challenge. One round involved remembering things from what was called a "classic TV clip". This was a scene from Emmerdale, in which a woman repeated the phrase "someone's knocked over a sheep".