DANCE Swan Lake, Piccadilly Theatre, London Romeo and Juliet, Royal Opera House, London

For reasons best known to the London theatre-going public, Adventures in Motion Pictures' West End run of Swan Lake has not been sold out every night. It was on Friday. Lynn Seymour, muse of MacMillan and the legendary Royal Ballerina was, at her own request, making a guest appearance as Siegfried's mother. Although her predecessors in the role have been excellent, Seymour, at 57, is able to invest the ageing nymphomaniac with a personality in which Catherine the Great meets Margaret Duchess of Argyll - whose society portraits Seymour rather resembles. Much of her success is thanks to her consummate acting. The frost she assumes on being introduced to the Prince's ghastly girlfriend is particularly fine - classical mime may not have had a gesture for "who is that slag in the puffball skirt?" but it sure as hell does now. However, Matthew Bourne's Queen Mother is not merely a mime role and Seymour also danced with a majestic sensuality well-matched by Adam Cooper's Black Swan. The comedy is equally delicious: her lascivious double-take when Cooper goes to kiss her hand but instead runs his tongue up to her armpit gets the biggest laugh of the evening.

Of course you should go and see Lynn Seymour in this show but the important thing is to see the show at all. A star cast is always good dinner-party conversation, but on Friday night, with the entire company on its mettle in the presence of Seymour, she was not the only star on stage.

Meanwhile, at Covent Garden, Miyako Yoshida was dancing MacMillan's Juliet, a role created by Seymour in 1965. Yoshida weighs in as one of those rather earnest Juliets (copyright M Fonteyn) for whom the coup de foudre is tempered by the knowledge that her happy little world has come to an end. However, Yoshida is a dancer who has always delighted in throwing herself into pas de deux with total disregard for personal safety. With a secure pair of hands like those of her new partner Irek Mukhamedov she can afford to do so, and the result was often exhilarating. She is generally more successful at romance than tragedy. She has a featherlight jump and a languid finish to every gesture; her whole body sings with happiness.

The orchestra was happy too, thanks to the acquisition of Viktor Fedotov as guest conductor. Alert and responsive, his beady eyes dart intelligently between the stage and the pit, serving the dancers as faithfully as he serves Prokofiev. In the "Cushion dance" the Kirov's maestro wrings all the arrogance and menace from the Capulets' show of strength. When pleased, he claps his baton for the dancers and kisses his fingers to the musicians. Any dull moments (trained critics have actually been known to power-nap through the crowd scenes) can instantly be enlivened by simply lowering your eyes to the demon at work in the pit.

AMP's `Swan Lake', Piccadilly Theatre, London W1. Lynn Seymour dances tonight, 30 Oct, 1 & 2 Nov. Call 0171-369 1734 for further casting details. `Romeo and Juliet' in rep at the Royal Opera House, London WC2. Booking: 0171-304 4000.