The first thing to know about Frederick Ashton's ballet, based on Potter's little books, is that he expressly didn't want it put on stage. "People will think I'm gaga," he is supposed to have said (this coming from one who later staged a work for peas and a cauliflower, but never mind). He had made a series of animal dances for the successful 1971 film, Tales of Beatrix Potter, and really didn't think they had any life beyond it. The Royal Ballet thought better, and in 1992, four years after Ashton's death, director Anthony Dowell rearranged his dances as a self-contained suite which has made a nice little Christmas earner for the company ever since.
The trouble is, Ashton was right. Although his choreography does supply the best bits of the film - in which it appears as visual asides to a spoken narrative - as a stage work it has to speak for itself. And it simply hasn't enough to say. For these are not the tales so much as the characters of Beatrix Potter, displayed in drastically telescoped versions of what happens in the books. (Peter Rabbit, absurdly, has only a walk- on part.) There is little chance for children to lose themselves in a story. And once we've finished ooh-ing and aah-ing at the thrilling verisimilitude of the animal costumes and masks, even Ashton's most inspired choreography struggles to provide the sort of substance that keeps young and old in thrall.
Most of the tales in this selection are pretty thin on incident anyway. What does Mrs Tiggywinkle do except sort through a pile of laundry? The fact that this fairly inert bundle of aprons and prickles holds the spotlight for two solo dance numbers, accompanied by the quaint plinkety-plonk of a mandolin, shows just how adept Ashton is at making much of little. And that - apart from pure nursery nostalgia, if it gets you that way - is the chief reason an adult might find to buy a ticket for this show.
Just as Potter does in her books, Ashton has struck a witty balance between human and animal behaviour that makes us appreciate both: the anatomical, magret-bearing qualities of Jemima Puddleduck, as well as the famous silliness, which is a human foible transferred. Her search for that convenient, dry nesting place is a brilliant piece of comic ballet mime, as she preens and fusses and waggles her tail-feathers before setting down her sagging rear with a satisfied whump. In the "Tale of Pigling Bland", the decision to put all the male pigs on pointe at a stroke turns feet into trotters. And the tender pas de deux between Pigling and Pigwig is truly touching, as Pigwig hoists her leg into classic arabesque and tilts her head towards the audience in the grand manner, before succumbing to a quivering, snouty kiss.
There is a supreme Englishness about Ashton's Tales - in its innocence, its restraint, its yearning for an idealised past - that puts it firmly in line with greater works in his output; works such as Les Patineurs, made more than three decades earlier, which the Royal Ballet once again includes to make a double bill. It's a good match, because although Patineurs doesn't make concessions to a junior audience, it again displays Ashton's delight in adapting non-dance movement to classical steps: in this case, imitating the movements of skaters on ice.
The illusion is so perfect, you'd think the Festival Hall had laid on a special slippery floor. Bodies are braced forward, feet slide, heads nod comically from side to side with each swishing step. Every few minutes, there's fresh pleasure to be had. Two girls do a cheery peg-doll walk on the tips of their toes. A fur-clad couple dance a dreamy love duet (too bad something went wrong here - she was giving him looks fit to freeze his face). A perky bell-boy does a Fred Astaire and nearly twizzles a hole in the ice. In short, they don't make 'em like this any more. And if you manage to spot that the entire work is made up of just five basic ballet steps, repeated, inverted, reversed, then good for you.
Royal Festival Hall, SE1 (0171 960 4242) to 3 Jan.