The 39 Steps is something else.

The fine-tuned farce is loosely based on John Buchan’s widely adapted mystery tale, starring just four actors using only basic props to recreate a frantic race against time and spies across the whole of Britain.

Each of the chameleon cast switches seamlessly and hilariously between the various characters portrayed in the plot, which follows the debonair Richard Hannay, falsely accused of murder, on the run from the law.

Not only that but he is also trying to disrupt the machinations of devious German secret agents attempting to bring Europe on the verge of a new world war.

The play revels in the inability of stage production to create believable effects.

From miniature trains to shadow-puppets, myriad hat swaps to floating windows, the 39 Steps  is imaginative, slightly ludicrous and frankly quite impressive.

But it is not just one long-running joke.

Easy laughs and potent gags aside, the foursome keep intact the adventurous spirit of the novel, never cheapening its story or becoming one-dimensional clowns themselves.

Gary Mackay and Tony Bell are as comfortable impersonating train passengers, policemen, spies, showmen, German double-agents and farmers as they are playing slightly stocky and most definitely masculine women.

Charlotte Peters is cracking as the various love interests of Hannay, portraying vulnerability and strength while showing true comedic abilities and often leaving the audience in stitches.

Richard Ede, the only cast member to retain his 'identity' throughout, brings an insouciant charm to Richard Hannay.

Turning a gripping spy yarn into a comic tour de force is no mean feat.

If it is true that laughing once a day keeps you healthy, then the 39 Steps will provide you with your recommended giggles fix for the rest of the year at least.