The Fitzrovia Radio Hour ** TNT

Sending up the behind the scenes workings of a 40’s radio show is a potentially fun idea which runs mercilessly out of steam in this Edinburgh festival hit.

One gets the picture pretty early on as, scripts in hand, the performers – their accents clipped, the women in tight pencil skirts, the men immaculate in bow ties and dinner jackets - create the parts and all the sound effects for not one, but three, pastiche melodramas, punctuated by ads, concerning a mummified undead queen looking for a new body to inhabit, Germans and Gay Hussars in India, and an ambitious man from Leeds who doesn’t know his place.

The rhythmic clack of coconut shells to simulate horses’ hooves, the crunch of cornflakes as an ancient body crumbles, and the various watery effects achieved with a watering can and a straw soon lose their fascination. Even the thwacking of a cabbage and squashing of a water melon (initially employed when a horse is decapitated) are repeated far too often.

At 30 minutes, this might have proved an enjoyable diversion, but, running far longer than the promised hour, this tedious show long outstays its welcome and had me longing for home and Radio 4’s Book at Bedtime.

Trafalgar Studios (2), Whitehall, SW1A 2DY Charing Cross tube (0844 871 7632) ambassadortickets.com/trafalgarstudios Till February 5 £20 (or £30 combined ticket with Barbershopera)