And so French and Saunders come to the end of the road. Winding up the TV sketch show after 20 years of mainstream success, the pioneering double-act has embarked on a tour that will give audiences what looks like being a final chance to savour a mix of greatest hits and new material.

It's to their credit that, for all its uneven qualities, their live performance still evokes the sense of mischief that set them apart from the wannabes at the beginning of their stand-up career. If you've always found their brand of humour somewhat hectoring - there is a hint of the eternal rag student about them - this tour will not do much to change your mind. For fans, though, all the elements are satisfyingly in place in an evening which efficiently blends some often wobbly live sketches and intricately observed video routines.

As you might expect, it is the taped media satires which work best. By the time Saunders has finished her parody of Madonna, preening herself in front of a dance studio mirror, her body bursting from an ambitiously tailored leotard, you almost begin to feel sorry for Madge. The same is true of French's wonderfully over-the-top impersonation of Catherine Zeta-Jones, all fecundity and four-letter words, as she waits to be summoned back to the boudoir by her insatiable husband. As for the spoof of Joan Collins and her sister Jackie, preening themselves as they swap self-regarding inanities, the satire is perfectly judged. This is the world of Hello! magazine as illustrated by Hieronymous Bosch.

Some of the send-ups are much cosier. Strictly Come Dancing poked gentle fun at Anton du Beke before French and Saunders, disguised as lecherous matrons, twirled across the Palace's stage in a display of wild-eyed one-upmanship. The rivalry between the two performers in fact is a central motif of the evening, French belittling Absolutely Fabulous (seen here in its very first sketch incarnation) and Saunders coming over all disdainful at the very mention of The Vicar of Dibley. That competitive tension, playful though it may be, becomes slightly oppressive after a while. The scent of ambition is always in the air, which makes it hard to warm to the pair simply as human beings.

The writing tends to creak most in the live skits, with repartee that is embarrassingly broad in places. The audience, it has to be said, obliged with belly laughs at the line "I'll kick you up the fanny". Overall, the physical details - the sagging posture of the old farmers arraigned in court, the mooning Devon vowels of the expats in Florida and the coy mannerisms of the two girls abandoned in a boarding school over Christmas - are more memorable than the scripts. It's good to see the two comics back on the road after such a long break, but they probably have chosen the right moment to call it quits.

In Manchester to Sat (0844 847 1722); tour continues at Sheffield City Hall on Tuesday .

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