This series has been described as "like parachute jumping where you can't remember if you're wearing a parachute", with comedians asked to improvise a routine based on a subjects presented on a screen, which they're seeing for the first time while onstage. Tonight, taking up the challenge are British stand-up Matt Kirshen, American comedian Eddie Pepitone and Robin Williams, doing continued penance for Patch Adams and a host of similarly excruciating films. This format transports him back to his roots.

He's best known these days as an Oscar-winning Hollywood film star but throughout his career Robin Williams (below) has been renowned for his stand-up comedy too. So he should be well equipped to survive the challenge of thinking up a new routine on the spot, with just a word or phrase to set him off on a stream of scatty humour. It's an interesting idea for a comedy show, with a laugh - or a cringe - around every corner.

'Asking a comedian to improvise an entire stand-up set is like asking a magician to do actual magic.' So say the creators of this fully improvised stand-up show of which this, the second episode, doesn't disappoint.

Comedy purists will love the pared-back nature of it - watching comedians in a dingy club, their fear palpable, sweating as they think on their feet. You'll gain a new admiration for comics too, as it exposes the finely-honed craft of a performer's routine. As Rufus Hound sagely comments: 'As long as you're hilarious, nothing can go wrong.' No pressure, then.

This week, American comedian Eddie Pepitone goes first, creating skits by responding to subject matter posted on a screen behind him. He doesn't fare too badly, though quick-witted Matt Kirshen, who follows him, nails it. Luckily, he's on before Robin Williams, who's such a presence and a pro that he'd captivate an audience of wild baboons. Expect to see the likes of Drew Carey and Ross Noble in upcoming shows.

If the thought of doing stand-up leaves you with clammy hands, then the premise for Set List will give you night terrors. Three stand-up comedians, in this case TJ Miller, Richard Herring and Frank Skinner, undertake the daunting task of doing an ad-libbed set based on topics which appear on a screen behind them. With no preparation and no trusted material to fall back on, what results is a nerve-wracking, frequently funny but ultimately inconsistent half-hour of comedy.

Much inevitably depends on the quality of the material they're given and some comedians are more at ease with the format than others (one imagines the likes of Robin Williams, Ross Noble and Greg Proops will flourish), but each of the comedians on display here manages to shine at times, most notably Miller. Watching seasoned comedy performers squirm under the stage lights as they rack their brains for funny ideas is strangely satisfying, though.

Frank Skinner, Richard Herring and US funnyman TJ Miller have willingly agreed to experience something that makes comedians break out in cold sweats - going on stage in front of a baying audience with absolutely nothing prepared.

That's the intriguing concept of Sky Atlantic's brand new comedy experiment Set List: Stand-Up Without a Safety Net, the appeal, of course, coming from the fact that some of the globe's top talents may crumble when forced to be funny on the fly. Being professionals, the trio put on what would be a damn fine comedy show in its own right, but it's the little 'oops' moments and the constant feeling that we're just seconds from disaster that elevates this form of entertainment that's been on TV since TV began into edge-of-your-seat stuff. It's genius, really.

The story behind Set List

James Mullinger met with the two founders of Set List, Paul Provenza and Babs Romen to discuss the runaway success of the concept.

Set List: an interview with Paul Provenza

Robin Williams has said it's the most terrifying, and awesome gig he's ever done. Richard Herring has described it as "cruel and wonderful genius", while Rich Hall has compared it to jumping out of a plane and hoping your parachute works.

Sky Atlantic recording review

Chortle reviewer Steve Bennett watches the show transfer from stage to TV.

Troy Conrad interview

Co-creator Troy Conrad developed the format with Paul Provenza first at the Comedy Central Stage in Los Angeles.