The Duffled Detective hasn’t been on our screens a great deal in recent years (well, unless you watch the Alibi channel a lot) but in the last few appearances there’s no denying Jonathan Creek’s felt like a very good magic act that you’ve seen one too many times. The illusion and its patter have started to become too familiar. Some of the greasepaint and wonder has rubbed away.

It’s a feeling repeated as you watch ‘The Clue of the Savant’s Thumb’, especially as the illusion at hand is one of writer David Renwick’s most used turns: the locked room mystery.

In a set-up that harks back nostalgically to many of the earliest episodes, and particularly borrows from ‘The Wrestler’s Tomb’, Franklin Tartikoff (Nigel Planer, who appears to have stolen Richard Wilson’s Merlin wig) is found dead in his study, only to vanish seconds later. And where’s Jonathan Creek? In the only real surprise of the episode he’s married and working in an office. It’d be less shocking to see him throwing pizzas at Paul Daniels.

It’s an interesting place to put Creek, a character who is as suited to working behind a desk as Alan Davies is to giving correct answers on QI, but it’s under-explored. Jonathan’s ‘Clark Kent’ life as an awkward exec is used as a corporate straightjacket escape rather than a piece of character development. Perhaps we’ll see it more when the show returns in the Autumn.

Some of the colour may have gone from his hair, but Alan Davies has lost none of the weary enigma he brings to the mop-headed genius, and spunky Joey Ross (the ever-delightful Sheridan Smith) is a fine counterpoint to his methodicalness. As the Scrabble-tastically named Rosalind Tartikoff, Joanna Lumley is breathy and pensive, like a thoroughbred recently spooked by a loud car,

But it’s the plot that’s the trapdoor under these performances. When Renwick’s ‘prestige’ moment arrives it is a tangle of weak motives; an ending that tries to tie too much together into one astounding ‘Tah-Dah!’ moment but makes a clumsy show of it.

Government agents, chainsaw accidents, political satire, wheelchair kung-fu… it makes you long for the simpler days of killer police jackets and alien skeletons made of mercury. So ludicrous is DI Pryke revealing that he had a jerry can filled with watered down apple juice that you’d have been forgiven for expecting Arrested Development‘s incompetent magician GOB Bluth to jump out, shout ‘Car trouble?!’, and accidentally squirt lighter fluid over everyone.

As a special, ‘Savant’s Thumb’ is ambitious but disappointing; lacking the ingenuity or the pervading sense of fear that other feature-length episodes like ‘Black Canary’ and ‘The Grinning Man’ have possessed. Pleasing though it is to see the Duffle Coat back on our TV, this is only a one thumb up effort.

Aired at 9pm on Monday 1 April 2013 on BBC One.

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Watch the trailer for the 2010 special…