It’s strange to reflect that Agatha Christie is now the only British playwright apart from Shakespeare to have a company dedicated to producing her work.

With the continuing success of Poirot and Miss Marple, her ingenious plots clearly retain their popularity, but then the process of television adaptation lends scope for moulding them to present-day expectations.

How do the stage plays themselves stand up?

The Agatha Christie Theatre Company’s production of Then There Were None struck me as a revelation in returning to its little-known, fatalistic original ending (though obviously not to its notoriously politically-incorrect original title).

For the company’s seventh outing its account of this 1953 courtroom drama, which was adapted for the cinema by Billy Wilder, no less (with Tyrone Power and Marlene Dietrich), is less convincing but still good in parts.

For example, one good part is the dimly-lit opening scene in chambers which is so evocative of the period that you can just imagine the pea-souper which would greet us if we stepped outside.

And it introduces Denis Lill as the grand QC Sir Wilfred Robarts – a wonderful, larger-than-life performance (albeit with one or two surprising rough edges) in the tradition of James Robertson Justice.

Not all the acting is as good as that, though, and when the action switches to the Old Bailey the shortcomings of Christie on stage as opposed to screen become apparent.

Even with a number of non-speaking extras this is an underpopulated court – only half a jury, for instance – and unlike the principals these characters don’t all look in period.

So there’s a real problem here with production values, despite the ingenuity with which policemen and court officers slip in and out to make quick-change cameos as expert witnesses.

That leaves us with what, to be fair, Christie is most famous for – the suspense, bluffing and double-bluffing of the plot.

Surely the nice and naive young man with the comically innocuous name Leonard Vole cannot really have bludgeoned a wealthy spinster to death for her money, despite the circumstantial evidence?

But if not, why is his very strange German wife apparently so keen to send him to the gallows?

If you don’t remember having seen the play or film before, the only way to find out is by going to see it now.

Rating: 3/5

Running time: Two hours, 25 minutes. Until Saturday (also Belgrade Theatre, Coventry, June 7-12).