I hope Mr Hall, the BBC's new Director-General, sat down that Monday evening and watched Jonathan Creek and quietly applauded. I can't remember a 90 minutes - actually I can, Doctor Who last week, but this one isn't really for children - I enjoyed so much. Oh, bits are always beseechingly silly. And it comes along so seldom that we're almost bound to enjoy it. But this was still a winning showcase for simple, entertaining, catch-all British drama. So we got a jaunty-spooky theme tune reminiscent of Harry Potter, we got Joanna Lumley, we got both Rik Mayall (still impossibly handsome and delightfully hammy) and Nigel Planer off The Young Ones, a body that had escaped from a locked room, Sheridan Smith playing feisty-naughty modern, as is her winning wont, another body felled by a gargoyle pushed off a mansion (that was Midsomer or possibly Wycliffe), some good gags about academics and, of course, Alan Davies.

His Jonathan is married off now (to the very sexy Sarah Alexander) and has, and you can't quite blame him, thus reluctantly had to put on a suit and get a good job in her daddy's advertising agency. For a few minutes he actually looks rather cool and rather suited in fact to both the Don Draper comportment and life. But soon, excuses combine to let him dig out the old duffel and go off to solve impossibly complex cases with the singular hangdog exuberance that holds the whole extraordinary thing together. Some serious bits, too, not least when Ms Lumley, playing a lifelong atheist, suddenly realises, and with a certain horror, that everything she has ever believed might not be true. This occasional series might not change the world, but it should change the way we remember just how solidly good simple entertainment on the BBC can be when it has the guts to go with its own happy formula.

With David Renwick's planned ITV sitcom frustratingly canned due to a creative dispute with channel bosses, Creek is the only outlet for one of the masters of TV comedy writing. The long-awaited Easter special saw Alan Davies and Sheridan Smith return, supported by Joanna Lumley, Rik Mayall and Nigel Planner, for a typically tricksy locked-room mystery.

You'd think that after 16 years and 28 episodes, Jonathan Creek might itself creak a little - how many more variations on the locked-room mystery can there possibly be? - but nothing could be further from the truth.

Plenty of fun is still to be had from the deliciously contrived plotting, melodramatic scenarios, star turns in supporting roles and sharp scripts peppered with neat comedy touches. Who cares that some of the exposition is so tortuous it borders on actor abuse?

A feature-length special, The Clue of the Savant's Thumb waits a full 15 minutes before the show's magician/sleuth hero makes an appearance. Instead, viewers are treated to a suitably overheated flashback preamble, set in 1968, involving sadistic nuns, hysterical teenage girls, stigmata, drug-induced visions and an unexplained death at a gothic mansion turned convent school.

And this was just the warm-up to the main event, in which the blood-drenched corpse of a legendary television producer disappears from the aforementioned locked room.

Alan Davies once again provides the calm centre around which all the mayhem revolves, with Joanna Lumley linking two of the three mysteries - writer David Renwick is never less than generous with his plotlines - and Rik Mayall still managing to deliver his trademark, wildly over-the-top performance, despite being cast as a wheelchair-using detective paralysed below the neck.

As I dozed during Jonathan Creek (BBC1), there was a moment of clarity. Such moments are created by a kindly god so you can finish crosswords or work out whodunnits. It became obvious who decapitated Nigel Planer and stuck the head on a scarecrow's body. It was Rik Mayall. The motive? Payback for those dismal veggie stews Planer's hippy Neil served Mayall's punky Rick in The Young Ones.

When I awoke, it became clear this hypothesis was wrong. The murderer could have been anybody but Mayall. Planer's smug polymath could have been rubbed out by his wife Joanna Lumley. Or terminated by her bit on the side so he could continue to marvel at Lumley's plummy articulation during pillow talk. Or by the usual suspects - sinister villagers, mad nuns, God. But not Mayall. He was the cop investigating the murder, after all. Hold on, though. Wouldn't that be perfect cover?

In any case, there were bigger mysteries. All those household names, all David Renwick's writing talent. For what? The disinterring of a three-years-cold corpse of a TV series whose historic function is to incite couples wending their way up the little hill to Bedfordshire to have exchanges such as the following. "Was it the crazed nun who reached through the portrait of Saint Barnabas to strangle Sheridan Smith?" "You idiot, it wasn't the nun. That was half a century earlier."

Renwick had a lot of fun with his script, though. There really was a character called Jacqueline Hyde, who didn't appreciate why Creek found her name funny. Planer's reading included a book called Cerebral Entropy in the Era of Fox News, though not its companion volume, Brain Shrinkage in the Era of Paranormal Hokum.

Jonathan Creek review: The Clue Of The Savant's Thumb

My only criticism of the plot, and it's a small one at that, is that it seemed to suffer slightly from 'additional ending' syndrome.

Review: Jonathan Creek: The Case of the Savant's Finger

The plot unravelled at the end, where a pointless layer of conspiracy was added to a well-worked mystery. Other than that, though, it was part Midsomer, part Sherlock, totally unthreatening.

Creek was a melange of highly watchable gobbledegook

A madcap plot that combined the supernatural, horror and detective genres to make a mélange of highly watchable gobbledegook followed.

Jonathan Creek: The Clue of the Savant's Thumb, BBC One

A gaggle of galloping thespians helps paper over the cracks in the plot.

Jonathan Creek: the Twitter reaction

From LSD and evil nuns to a political satire gone wrong and a severed head inside a globe - here's what you thought of last night's Easter special...

Jonathan Creek intrigues 7 million viewers for BBC One

Jonathan Creek returned to BBC One on Easter Monday (April 1) with impressive ratings and beat ITV's Broadchurch in a head-to-head detective drama battle.