It began with a stage version by North Country Theatre artistic director Nobby Dimon; then Patrick Barlow brought his comic skills to the West Yorkshire Playhouse in 2005 to adapt John Buchan's spy-thriller novel, Alfred Hitchcock film and Dimon's original vision.

The adventures of Richard Hannay have since transferred to the West End, Broadway and now Australia, and a touring production is on its way to York Theatre Royal on Tuesday. Charles Hutchinson fires off questions to Australia, where director Maria Aitken is in rehearsals once more.

Why do you think this stage version of The 39 Steps has caught on in Leeds, London, America and now Australia, Maria?

"Its humour would seem terribly British, so what makes it work overseas too? It's caught on in Israel and Italy too, where this production is still running, and it's due to be done in Korea in the summer. All very thought provoking.

"I think everybody likes an innocent on the run, hence the international success of Hitchcock films - that idea speaks to something pretty primal. And each country has its amused attitude to the character of a stiff-upper-lipped British hero.

"From a purely theatrical standpoint, I think watching four people dementedly keep a story afloat without expensive scene changes, but with their bodies, three trunks, two ladders and some smoke... well, that's a homage to the power of theatre.

"I think people are tired of trillions being spent on musicals which leave them unsatisfied - this way, they get their money's worth by watching sheer human endeavour.

"And though it's hugely sophisticated comedy in one way, it's also innocent and childlike - and appeals to all ages."

What are the characteristics of Patrick Barlow's writing that makes his skin-of-the-teeth humour so distinctive?

"That he works on two levels: the story-telling and the actors telling it - the actors, not the characters.

"The glimpses of the offstage world that he uses to punctuate - the actors' hierarchy and a theoretically incompetent stage management - that's all there bubbling under the surface. We don't see it often, but it's a grand and funny theatrical shock when we do. The other thing is that he has fantastic rhythm."

As a director, how much do you have to stick to Patrick's template of few actors taking on seemingly impossible theatrical odds to deliver a play safely home, or can you veer off-piste and on to the black run for even more thrills of your own?

"Quite a bit of off-piste, but always with his approval and collaboration. When I came on board I asked for some rewriting, and we also made some changes for the Broadway production. When it comes to the actual staging, that's for me and my movement director. But it has always been and will always be a collaborative endeavour."

When The Press interviewed Patrick in 2006, he was adamant his theatrical interpretation of The 39 Steps was not a spoof. In particular, he said the story of Hannay, lost and depressed at 37, was as important as the lunacy and adventure. Would you concur?

"I would in principle, and we have plundered the film for all its romantic journey between Pamela and Hannay. And Hannay, after all, tells the story.

"But in practice, the lunacy and invention of the two men who provide all the other characters can sometimes overwhelm things, particularly when the director is away doing another production. But we try to keep a tight eye on things, with Patrick and me and the producers and the assistant directors dropping in wherever geographically possible."

  • The 39 Steps, York Theatre Royal, Tuesday to Saturday, 7.30pm plus Thursday, 2pm, and Saturday, and 2.30