Next year, Hercule Poirot will achieve something that Sherlock Holmes never managed.

Although the pompous Belgian with the waxed ‘tache and the surfeit of little grey cells will never be the equal to the Great Detective of 221B Baker Street (he’s more of a Mycroft, if anything), 2012 will see David Suchet, the greatest small screen incarnation of Agatha Christie’s finest creation, complete the entire canon of his character’s stories, something that Jeremy Brett – the finest Sherlock of them all – never accomplished.

Yeah, pedants can quibble about a couple of minor tales that will never be Sucheted, but it’s still as close to a complete set as anyone is likely to get. And although it has lost the spookily bizarre avant-garde opening titles, the marvellous theme music, the art-deco sets, and a lot of the quirky humour during its twenty-two year stint (immortal exchanges like ‘I’ve got a parrot here for Mr Poyrott’/ ‘It’s pronounced Poirot’ / ‘Beg your pardon, I’ve got a poirot here for Mr Poyrott’ are mostly a distant memory nowadays) the show is still almost as enjoyable in its dotage as it was in its fair flush of youth.

The Clocks is standard convoluted Christie fare under the auspices of ITV: a period police procedural with hints of political intrigue and a romantic twist.

The two principal plot strands – naval espionage under the looming shadow of World War II and the mysterious discovery of a body in the house of Miss Pebmarsh (Anna Massey in her final on-screen performance) by a young typist, Sheila Webb (Jaime Winstone), who also finds four clocks set to 4:13 – only cross over tangentially during the course of Poirot’s investigations.

The detective is called in by a friend, Colin Race (Tom Burke) to investigate the former but ends up taking an interest in the latter, to the chagrin of Inspector Hardcastle (Phil Daniels), who despite an almost anachronistic interest in criminal profiling for a cop in 1938 finds the methods of Belgium’s finest a little difficult to comprehend.

‘I do not think it important who he is, but who he is,’ Poirot cryptically comments on the corpse. To his departing back, a bewildered Hardcastle does a sarcastically convincing impression of the elegant sleuth. It’s like Inspector Japp never left. (Poirot’s relationship with the significantly younger Race, however, leaves one lamenting the departure of Captain Hastings – happily for fans of Hugh Fraser, the captain is returning for Poirot’s last bow next year.)

As ever with the series, the production values are as high as the man who mucks out the latrines in the Green Field on the last day of Glastonbury. The summery Dover setting is an out-of-season seaside scene for Boxing Day but it evokes the spirit of 1938 as well as it captures the distant warmth of coastal sun.

The sequence in which Poirot and Vice-Admiral Hamling (Geoffrey Palmer, bringing his usual gruff magnetism to the role) stand at Hellfire Corner, looking out over the sparkling, sun-soaked sea and discussing the war they both fear is approaching, is a highlight of the episode which has much to do with the location as the veteran actors’ performances.

Elsewhere, the secret tunnels beneath Dover Castle provide a gloomy peak into the world of between-the-wars MI6 while Colin Race’s upper lip – which never wavers even when he finds a stolen clock and a bloody knife in Sheila Webb’s bag – is so ramrod stiff it must have been knocked up by the scenery department.

However, despite the stellar supporting cast, the setting and the story, Agatha Christie’s Poirot is ultimately the Suchet show; and the principal actor doesn’t disappoint, even though – or perhaps because – he knows the character so intimately he could play him in his sleep.

Poirot’s mannerisms, from the way he holds his glass of wine to the touching of his hat to a lady, and his unconsciously patronising superiority, appear effortless to David Suchet after so long, but he keeps them fresh by never once acknowledging how faintly ridiculous Poirot is.

The absolute faith he has in the character – even when little girls are chiding the hallowed surname: ‘That’s not a name … it’s just a noise’ – suspends any disbelief like a jammed venetian blind. The elaborate exposition at the end (as slow-paced as the rest of the story, but that’s hardly a cause for concern on Boxing Day, the most languorous day of the year) encapsulates everything about this enduring character and the man who brings him to life – both slightly rounder and more wizened by the years, but still as entertaining as ever.

Aired at 9pm on Monday 26th December 2011 on ITV1.