"It all grows out of our merciless piss-taking of each other," says Toby Park (above, left). "Petra is extremely dense with the most fantastic talent for malapropisms.

According to the others, I'm the good looking but rather boring one. Aitor is fat and lazy. And Stefan how can you mock Stephan? Well, he's the German."

Bridging their cultural and linguistic diversity with a shared penchant for taking silliness to the extreme, Spymonkey are a Brighton-based physical comedy group with an impressive international reputation.

Having met in 1997 while working with a Swiss action-theatre group, they conceived Spymonkey on top of a French mountain and premiered their first show at Komedia a year later.

Now they're debuting an extended version of their second hit, Cooped, a deliciously demented pastiche of a pulp gothic novella, and hope the Theatre Royal will provide the ideal setting.

"The main angle of the show," explains Park, "is of one of those terrible rep companies completely overreaching themselves."

Set during the Sixties in the dilapidated ancestral manor of Birch End, Cooped follows the fortunes of the innocent young fille Laura du Lay, who takes up the position of confidential secretary to the reclusive Forbes Murdstone.

"It seems he has a personality disorder," says Park, who claimed the role of this broodingly handsome aristocrat.

"He's all nice and romantic one minute and a psychopathic murderer the next.

"Laura's bewilderment expresses itself in these strange seizures where she has weird visions allowing us to wander off into some very unexpected places."

These include a choreographed boy-band number, an extended fart gag, and the appearance of some dancing pheasants.

Now reworked into "a complete monster with so many tricks to the scenery it takes two days to set up", Cooped was originally devised by Spymonkey's writer/director Cal McCrystal, who drew on his childhood love of a Seventies American gothic soap called Dark Shadows.

"It had very tacky production values and the ridiculous shooting schedule meant everything would have to be taken on first shot," recalls Park "So you'd get fantastic wobbly sets and flies flying into actors mouths just as they were about to deliver some warlock curse.

"But Cooped comes out of affection," he adds. "It's not really parody or satire, because they're all about being cleverer than the material and we're never ever cleverer than our material."

Starts at 8pm tonight, times vary. Tickets cost £6-£15, call 01273 709709