Who would have thought The 39 Steps could be so funny? Sure, the 1935 film has its moments of campery - how could it not with Hitchcock in charge?

But John Buchan intended his original book to be "a shocker" - a tense thriller mixing political and personal drama with action that is so far-fetched, readers would barely believe it could happen.

In Maria Aitken's production - which opened a new season at Richmond Theatre this week - the audience barely stops laughing. And not just with relief that the panto season is finally over.

From the get-go, it is clear why the show won Best New Comedy at last year's Olivier Awards. Aided by Patrick Barlow's adaptation, Aitken's first good move is to revel in the datedness of Buchan's story, in particular its stiff-upper lip hero, Richard Hannay.

David Michaels delivers Hannay's cut-glass vowels and raised eyebrows with self-knowing glee, signalling to the audience that he and the rest of the cast are in on the joke.

And Clare Swinburne is sexy and poised as his sparring partner and love interest, first in the role of German spy, Annabella Schmidt, and later as good old English gal, Pamela.

Particular mention must go to her leg muscles which hold her in place as a corpse for a good 10 minutes at least.

Physical strength and stamina play a big part in the production -with just four actors on set there is a lot of work, but they re-enact every last train journey, bridge crossing and car chase of the book with gusto. Never have props been put to such good use.

Holding it all together are Colin Mace and Alan Perrin, a pair of old-fashioned clowns who play every part going, good guys and bad, from spies in the street and Nazi academics to a couple of tartan-clad Highland hoteliers. In the final scene, Mace even conducts a police interview with himself.

While the pace is quick, what you do lose in this slapstick approach is some of the tension. But no matter, our stomach muscles were already aching enough.

A woman sat behind me on the opening night had seen the West End show and vouched for the fact that it was just as funny second time round.

"Not what you would expect from Maria Aitken," she said, and I guess she is right. Nice to see the upper classes not taking themselves too seriously.

Best of all, Aitken has reminded us what theatre can be at its inventive, energetic best: pure entertainment.

The 39 Steps is at Richmond Theatre until Saturday, January 26. Call 0870 060 6651, visit richmondtheatre.net.