Monty Python, O2 Arena

It could have been an embarrassment all round; a bunch of blokes in their seventies revisiting material that was anarchic and transformative 40 years ago but which they are now performing for 10 lucrative nights in the home of commercial comedy. Fear not, though, Monty Python Live (almost): One Down Five to Go – surely the final farewell tour – proves that quality endures.

The original television show, Monty Python's Flying Circus, aired on the BBC from 1969 to 1974 and the sketch group – Idle, John Cleese, Michael Palin, Terry Jones, Terry Gilliam and Graham Chapman (who died in 1989) – regarded as the comedy equivalent of The Beatles, went on to make highly successful films, including Life of Brian. They last performed together in 1980, at the Hollywood Bowl in Los Angeles.

Like all reunions, this one is tinged with sadness as the “one down” is remembered at the top of the show; in typical Python fashion, any toe-curling emotion is dispensed with as a Gilliam cartoon has Chapman's head kicked into outer space, where it lands on a police telephone box, the Retardis. The Retardis then appears on the stage – which is kitted out like a Victorian music hall with velvet swags, a curved staircase and decorated by cherubs - and out pop the remaining five.

They kick off with The Yorkshiremen (actually not technically a Monty Python sketch, but one they have always performed at live events), and it sets the tone. “Who'd have thought, 40 years ago, we'd be sitting here doing Monty Python?”, one of several knowing self-references of the evening - including a “merch-o-meter” flashed up on the three huge on-stage screens during the interval, indicating how much more dosh the troupe are making from the merchandise

All the old favourites are performed - the Bruces, Blackmail, the Spanish Inquisition - some with tweaks, others given a big musical treatment, performed by the 20-strong ensemble (as with the Ministry of Silly Walks, which Cleese is no longer able to do), with choreography by Arlene Philips and a kicking band under the direction of John Du Prez. But Idle knows when to keep things simple; there's a straightforward rendition of The Lumberjack Song, with Carol Cleveland as the girl who finds her beau rather less butch she had imagined.

Monty Python's Flying Circus often dispensed with punchlines, seguing into another sketch, cutting to one of Gilliam's cartoons, or having the action interrupted by one of them saying “and now for something completely different”. Here, Idle moves the action seamlessly from one sketch to another by having a cast member walking away from one set-up stage right to another stage left, or plays videos of original TV footage, such as the Fish-Slapping Dance or the Philosophers' Football Match.

He also drops in some neat visual jokes - aimed at Vladimir Putin and the Top Gear presenters - and there's a very funny video insert in which Stephen Hawking uses his speeding wheelchair to silence a gabbling Brian Cox, banging on about the universe during Science Today.

There's the occasional misfire or dip in pace, and a couple of sketches, such as Spam and Mr Anchovy (which sets up The Lumberjack Song), felt underpowered last night. But the material stands the test of time and the performances grow stronger as the night progresses. Some sketches, such as Michaelangelo meeting the Pope (pictured above), and, thankfully, the Dead Parrot - are triumphant in a highly entertaining show lasting nearly three hours.

The encore is, of course, “Always Look on the Bright Side of Life”, and last night's audience – most of whom were not born when the original series ran – filed out still singing it, feeling they had been part of a little bit of comedy history. 

• Monty Python are at the O2 Arena until 20 July