Towards the end of last year’s Edinburgh festival, the Dutch Elm Conservatoire were so depressed, they were almost ready to jack it all in. The audiences just hadn’t been showing up. Reviewers had been in, but somehow their views hadn’t made it to the page. Every day, the boys passed through the Pleasance Courtyard and saw the board listing shows “sold out for tonight”. Their gig had never been on it. With less than a week to go, they resolved to make one last desperate push.

“We spent £25 on staples for flyers, and were getting ready to traipse round town with them,” explains Renton Skinner, one of the troupe’s founder members. “Then, the next morning, we had been nominated for the Perrier award. We had as much press as we wanted for free, and our final five days sold out overnight.”

In one of those gooey Edinburgh success stories, the group have secured a development deal with the Who Wants to Be a Millionaire producers, Celador — which is richly ironic, as the nominated show had been specifically developed for an unsuccessful Radio 4 pilot. Now the show, Conspiracy, is touring arts centres.

Part comic play, part sketch show, Conspiracy has a beautifully ludicrous plot — The Goodies meets The X Files. The quintet are running a conspiracy-theory investigation company from the throbbing heart of Bracknell. Unsurprisingly, things aren’t going well financially, so they each embark on a different piece of slapstick skulduggery. One takes an assassination job in Moscow (“What can I say, Gene? Jack Straw loved your head shots”), which goes so badly wrong, he has to be swapped back for a more successful Russian agent, with the KGB throwing in a BMX to sweeten the deal.

There’s a high-farce exposé of the moon landings, built on the premise that — to cut costs — Nasa shot fake footage at Pinewood studios and Buzz Aldrin didn’t get to go first because his American accent sounded too Welsh. Meanwhile, a Nazi plot to reanimate Christ from DNA on the Turin shroud is foiled, aliens land in Sting’s back garden and one member of the team hires a Columbo lookalike from The Stage newspaper to find his daughter, thinking it’s the real Columbo. Finally, when everything seems at its lowest ebb, they re-enact Princess Diana’s death in a high-tempo finale and discover that it was all a plan for Paul Burrell and James Hewitt to secure “lucrative yet degrading” reality-TV contracts.

Dutch Elm’s success highlights a new trend in the UK’s complex live comedy scene. The fivesome got together as jobbing actors looking for a creative outlet, and cut their teeth in a burgeoning sketch community that has been quietly building over the past few years in London pubs and fringe theatres, including the Betsy Trotwood, in Farringdon; the Hen and Chickens, in Islington; and the Etcetera Theatre, in Camden. Coagulating around the skit duo Oram and Meetam, it has produced Radio 4’s The Consultants, American television’s unlikely hit show The Hollow Men and 2005’s Perrier-winner, Laura Solon. “People were finding it hard to go on and do five minutes of character in a line-up of comics in a drunken boozer,” Stephen Evans explains. “Now, the community has developed its own venues, to have a safer environment to try stuff out in before you’ve got a full hour of material.”

Evans is one of the original trio — along with Skinner and Jordan Long — who founded a dubiously monikered sketch outfit, The Benders, in 2000. After the initial incarnation collapsed, they re-formed as Dutch Elm, with Rufus Jones and the television writer Jim Field Smith. “There’s so many of us because we weren’t sure that everyone would turn up to rehearsals,” says Smith. “We thought we’d be the Blazin’ Squad of comedy.”

Their 2004 Edinburgh debut was a well-received but conventional sketch offering. It wasn’t until Radio 4 started nosing around that the group started mixing sketches and narrative. They took the idea for Conspiracy from a shared love of overblown 1970s action films such as The Wild Geese. “The show is littered with conscious nods to those hugely contrived spectaculars with Richard Harris running around the jungle killing unnamed Africans,” Skinner says. “They ’re hilarious, and much more of an influence than whatever David Walliams and Matt Lucas are doing. I think you’re more likely to get that from people with an acting rather than a stand-up background. The League of Gentlemen were actors, and their influences were horror films. We took what we liked and made it funny.”

Plenty of critics are clutching their heads: five white middle-class men, one with Footlights experience, embarking on intricate, sketch-related comedy. “We’re not doing ourselves any favours,” says Jones. “We’ll live or die on the quality of the writing. We have to hold people for an hour with a relatively complex show.

“That’s the beauty of using conspiracies — they have an inflated sense of their own importance, which gives us the melodrama, but at its heart it’s a show about a group of men doing something utterly pathetic.”

Tour dates at www.dutchelm.co.uk