Down the road, Ewan McGregor is playing to full houses in Guys and Dolls.

Nearby, Friends heart-throb David Schwimmer takes the lead in Some Girls.

But at the Criterion theatre in London’s West End, the star is a large hairy beast, with purple spikes on his back and a wart on his nose.

The Gruffalo is based on the best-selling children’s picture book by Julia Davidson and Axel Scheffler. It tells the story of a quick-witted mouse who outsmarts various predators by telling them that he is meeting a fearsome Gruffalo for tea. When the Gruffalo eventually appears, the mouse convinces him that mice eat Gruffalos for their tea.

From the 24-page book, director Olivia Jacobs has achieved impressive feats of characterisation. There is the fox, whose cloth cap and sideburns lend him an uncanny resemblance to pro-hunting campaigners. And the owl, in Biggles helmet and airmen’s goggles, that uses an air-raid siren to sound “mouse alert”.

The plot, too, is filled out admirably, with exuberant songs and look-behind-you audience participation. But none of this can detract from the disappointment of the Gruffalo himself.

Despite a hairy monster costume, there are no huge teeth, and his wart is barely visible from the stalls. His face, in fact, is entirely human. Most small children have read the book; surely a sharp-tooth mask would not generate too many nightmares? Ewan McGregor need not fear for his position as leading man of the West End just yet.

The Gruffalo is at the Criterion until August 21, and on tour through the summer and autumn. www.tallstories.org.uk