See How They Run - Agatha Christie spoof is delicious cinema fun

You get the feeling that the entire company had great fun making See How They Run. The great news is that you will have just as much watching it.

There is a lovely lightness of touch about the whole thing, backed up by laugh-out-loud wit, delivered by a fabulous mix of slightly larger-than-life characters – a bunch of actors sending up actors and acting in a glorious Agatha Christie spoof set behind the scenes on Dame Agatha’s monstrously successful Mousetrap.

It’s early days in the play’s astonishing run. In fact, we are back in the early 50s. The play is celebrating its 100th performance – and the film-makers are gathering. The trouble is, so it turns out, the film can be made only once the play’s run is over.

What could possibly stop it? The murder of the hovering film director, for a start, Adrien Brody delivering a wonderfully brattish swine of a film-maker certain to turn everyone he comes into contact with into a potential suspect in the event of his demise.

It’s a whodunnit and there are plenty of candidates lining up, from the uptight pompous writer Mervyn Cocker-Norris (David Oyelowo) to a slightly under-used Reece Shearsmith as producer John Woolf, from impresario Petula Spencer (Ruth Wilson) to… well, just about anyone in the 50s theatreland the film so beautifully evokes.

It’s a delightful mix of characters, each with their own motives and secrets, each clashing with the other.

But maybe the thing above all that ensures the success of the film is the police pairing brought in to solve the dastardly crime.

Sam Rockwell is brilliant as the world-weary Inspector Stoppard; and the super garrulous trainee Constable Stalker – deliciously played by Saoirse Ronan – is precisely the partner to make him even wearier with his world.

He would far rather slouch off to the pub than solve a crime; she meanwhile is scribbling down absolutely everything for fear of missing the one thing that actually matters.

It’s a dream combination in a film which is consistently funny, a rich wit running right through it, great fun too coming courtesy of Tim Key’s Commissioner Harrold Scott.

There is a super-abundance of clues – plus plenty of in-jokes and allusions. We’ve got a Stoppard, for instance, and a near mention of The Real Inspector Hound. Stalker is still a name to conjure with in police circles. And doubtless there are countless other little references you’ll do well to notice, not least in the mentions of the Rillington Place case which has swallowed up all the manpower, leaving Stoppard alone with his Stalker.

It's a film which hits the ground running, instantly intrigues and amuses and, best of all, doesn’t run out of steam as the on-stage events of the Mousetrap start to find an echo in the off-stage events which conclude the film at the great Dame Agatha’s Berkshire mansion.

Her own mysteries come home to roost, with Shirley Henderson superb as the great Dame herself.

She certainly finds herself on the end of one of the film’s finest lines when the villain grabs her towards the end.

Probably none of it is going to prove terribly memorable, but who cares: it’s cracking fun while it lasts.