Best known as The Congress Of Oddities, Margaret Cabourn-Smith and Zoe Gardner have sneaked into the Fringe this year with a free show that doesn’t feature their names in either the title or programme blurb. But while An Hour Of Telly: Live! might be a low-key, work-in-progress, there’s more to enjoy here than in many allegedly ‘finished’ sketch shows at the festival.

The title suggests a fairly traditional selection of TV parodies, but the difference here is that the duo admit from the outset that they don’t really watch the box, so the ensuing 40 minutes is ‘pretty much based on guesswork’.

That doesn’t stop them nailing the stilted, scripted dialogue of cheap adverts, the vacuous ‘have your say…’ interactive segments that devalue the medium, or the telethon’s uncomfortable bedfellows of charity and entertainment. But in not being constrained by mocking genuine broadcast output, this charming duo have the ideal opportunity to just mess about, as demonstrated by their bartering with the audience’s possessions, because that’s what they think Bargain Hunt is probably all about.

Some of the scenes are madly surreal, yet with a twisted logic that stops them spinning off into randomness; while the pair’s finest techniques is for the sudden overreaction – a violently barked line bursting out of nowhere, shattering the mood of the scene. It’s one of these moments that provides possibly the single funniest line of the month, even if its use of the C-bomb and reliance on context means it was sadly overlooked by the pun-loving viewers of the Dave channel. But that offbeat insult alone wins them an extra star on this review.

Versatile Cabourn-Smith gets to show off her full range in a mightily impressive parody of West End musicals – appropriately enough, since she’s also in Gutted! at the Assemby Rooms – while few people do distant otherworldliness like Gardner, who here manages to be both grounded and away with the fairies, sometimes in the same sketch.

An Hour Of Telly looks set for great things when it’s finished – but even now, when it’s for free, it’s a solid piece of ridiculous entertainment.