Old theatrical war horses don’t come any older, warty or horsier than The Mousetrap. The longest running show in the history of theatre has recently licenced a national tour alongside its 63rd consecutive year in the West End.

A tricksy whodunit based on interconnecting rooms and interconnected characters who mostly have something to hide, The Mousetrap persists in inviting the collaboration of audiences not to give away the plot. Instead I can offer two things: firstly the succession of dark overcoats, light scarves and soft felt hats in the opening scene is a red herring, and second my mother’s observation that “she cheats” as Christie consistently introduces a crucial piece of evidence three quarters of the way through the structure to defeat the ability of readers or audience to guess the outcome.

Indirectly, The Mousetrap begat Gandhi. Richard Attenborough first played Sergeant Trotter and took a 10% share in the production instead of full salary. Thirty years later, he sold it to help finance his film. Coincidentally because the production forbids a UK film version until six months after it closes, the only movie derivative is a Bollywood one Chupi Chupi Aashey.

The solid country house set – this touring version cost £50,000 – and comfortably upper-middle-class characters where no one has an actual job and everyone has time to ‘write letters in the morning room’ belie the fact that Agatha Christie based her short story and then the play on one of the blackest episodes of fatally sadistic child abuse ever recorded: it was the 1945 equivalent of the Baby P case and led to new legislation on fostering. If you could re-write it with Sharon Shoesmith replacing the Mrs Boyle character, it might have shockingly contemporary impact.

There’s an entire PhD thesis to be written on prejudice and snobbery in Christie, but any TV Marple or Poirot confirms them. Her favourites biases are here represented by a retired major, a fortunate heiress, and the three clunking great stereotypes on whom suspicion first falls: a highly-strung effeminate man named Christopher Wren, the ‘mannish’ Miss Casewell and token foreigner Mr Paravicini. Even allowing for the differing mores of 1952, the Manchester Guardian reviewer found them ‘built entirely of clichés’.

There are only two ways to play such a vintage piece: ‘dead straight’ or with heightened and controlled over-acting, for laughs. Director Ian Watt-Smith seems unsure which to favour, as Oliver Gully as Wren and Gregory Cox as Paravicini opt for startling vocal projection and extravagantly camp gestures, while Anna Andresen as guest house owner Mollie Ralston, Louise Jameson as sternly disagreeable Mrs Boyle and Amy Downham as an elegantly sapphic Miss Casewell strive for as much naturalism as their stilted dialogue allows.

There’s a lot of painfully slow exposition in Act I but everything improves with the pivotal arrival of Lewis Collier as a refreshingly credible and authoritative Sergeant Trotter and he carries both the audience’s suspension of disbelief and the play to its twisted, rather than bitter, end.

A further curse of The Mousetrap is that, despite having its West End cast renewed every November and more than 4000 actors covering its eight roles here and abroad, it scarcely made a star of any of them. I know two promising actresses who each played Miss Casewell: one runs a ticket agency, the other’s a speech therapist.  In Coventry.

At the Lighthouse Arts Centre in Poole, it has to be said, the Saturday audience lapped it up.