Last Night's Viewing: Felix and Murdo, Channel 4<br />It'll Be Alright on the Night, ITV1

Watching other people laugh is a funny business. It can curdle the hilarity in you in an instant or make it impossible for you not to join in, and it isn't easy to say what makes the difference. There were at least three sets of contagious laughs last night – one of them performed in Felix and Murdo (a Channel 4 one-off that is looking at the commissioning editors with liquid eyes in the hope of an extension) and the other two separate bouts of inexpertly suppressed giggles in It'll Be Alright on the Night, on which Griff Rhys Jones now has the task of reading out the mirth-killing autocue gags. And, while I would have bet on the latter to get anyone going in the end, it was the former that was actually more impressive. Trying not to laugh when you really, really want to is something pretty much any of us have done at one time or another. Pretending to laugh uncontrollably when you don't want to (and making it convincing) is a much rarer skill.

Felix and Murdo gets quite a long way on the performances of Ben Miller and Alexander Armstrong, who did a bravura bit of tittering in the middle of this spoof Edwardian tale, having taken drugs as part of Murdo's training regime for the 1908 Olympics. But Simon Nye's script turned out to be pretty lively too. Sometimes his name on the credits means you brace yourself for something safely middle-of-the-road, but every now and then, as here, he abandons sitcom's shallow end to do something more free-form and gamey. Armstrong plays Murdo, a languid toff whose butler cuts anything "depressing or bothersome" out of the paper before handing it over, while Miller is Felix, a banker with a sideline in mad inventions. Murdo hankers after Felix's suffragette sister, Winnie, while Felix himself is enjoying vigorous "outercourse" with his fiancée, Fanny, a woman who protects her virginity by permitting every other liberty imaginable. "Good old anal," says a satisfied Felix, after popping upstairs with her. "Always goes down a storm."

It's recognisably Blackadderish in its approach to history, silly and inventive and with a good line in visual gags. Felix complains to his intended that her parents don't really like him. "Where do you get that idea?" she protests. "My birthday present," he replies, at which point the camera cuts to a framed needlepoint sampler on the wall reading, "We loathe and despise you". It pauses for just long enough for us to take it in before sliding down to a larger one below that reads, "For the Love of God Fuck Off". The comic pace perhaps slowed a little as it reached the 20-minute mark, but I have a feeling that it only felt that way because they came out of the blocks at such a sprint in the first half. I'd happily watch more.

Griff Rhys Jones also brings a rougher edge to It'll Be Alright on the Night, with jokes that Dennis Norden probably wouldn't have felt comfortable with, though he employs that same irritating chuckling-as-I'm-talking-because-it's-so-irresistibly-funny delivery. A series that started out when YouTube wasn't even a twinkle in Chad Hurley's eye now has to live with the fact that some of its best clips have already gone viral, as was the case with Bradley Walsh's heroic attempt to keep a straight face as he asked a question about Fanny Chmelar and that hapless Australian reporter who tried to tell the Dalai Lama a lame Dalai Lama joke.

But there are still in-house clips that work. Ant and Dec made me giggle by being unable to stop themselves and, while I already knew that Kim Woodburn got fearsome drunk in that Celebrity Come Dine with Me, I didn't know quite how drunk until last night.