A sumptuous 'Swan Lake' by the London Festival Ballet

The tiny, wide-eyed ballerina, swathed in a dark-green dressing gown and still sporting the sparkly crown of the Swan Queen, greeted her husband and guests outside the dressing room, bubbling with joy.

In German, Russian, and English, she was congratulated on her just-ended performance in the double Odette-Odile role in the new London Festival Ballet production of Tchaikovsky's ''Swan Lake,'' staged by John Field, the company director.

Without any sign of exertion or tiredness, she led the group into the dressing room, sat down in front of the bright mirror, and began to remove the crown while guests bustled and chattered around her, toasting her success.

Galina Panova had been invited by Field to star in three productions of ''Swan Lake'' -- underscoring the fact that, with this latest production, there were now four different versions of the ballet in the British repertory.

The Royal Ballet has one, the Scottish Ballet another, and there is the year-old version by the Sadlers Wells Royal Ballet. The Festival Ballet's new one is the fifth it has produced since 1965.

Ballet critics here are virtually unanimous that there was no need for another redoing of the classic work, especially since Field has neither shortened nor added anything brilliant to the original Petipa/Ivanov staging of 1885.

The critics would have preferred to see the money spent on the last two revisions put to financing more touring by the major ballet companies throughout the United Kingdom. Sadly, a ballet like ''Swan Lake'' is often too large and elaborate for provincial theaters.

Before Panova took over the lead, the latest Festival Ballet production was poorly received here. Yet the production I saw, although too long and vague in parts, was an interesting one. On the whole, the audience enjoyed it. Panova brought to her role the technique and virtuosity that won her the gold medal at the Varna (Bulgaria) ballet competition in 1970, under the tutelage of the legendary Galina Ulanova.

A graduate of the academy in Perm in the Ural Mountains (itself established by Bolshoi graduates from Moscow), she joined the Kirov company in Leningrad and danced with her husband, Valery Panov, until both applied to emigrate. Their careers almost ended under persecution by the KGB.

After not being able to dance -- or even to rehearse -- for almost two years, they were finally permitted to emigrate, helped by a massive public campaign in England and the United States. Today they dance all over the world, and Valery Panov is also recognized as a talented choreographer.

For the audience, the Festival Ballet ''Swan Lake'' is spectacular, even if it does last 3 hours and 20 minutes, 5 minutes longer than even the Bolshoi production in Moscow.

Costumes by Carl Toms are sumptuous -- velvets and brocades in beige, brown, and olive-green in the first act, and deep burgundy and gold, white trimmed with white fur, and dark greens and gold for the character dances in Act III.

The swans are taken out of their tutus and put into longer tulle skirts: In reality, the Prince really need not scrutinize the entire flock while searching for Odette.

The plot is changed somewhat and weakened. A prior knowledge of the ballet is a great help. The mime is more pronounced, but some important moments are missed if one does not stare intently at the right place at the right time.

For example in Act III, Odette's pleading at the window as the Prince vows eternal love to Odile is such a fleeting vision, before she is hidden by Von Rathbart's cloak, that many in the audience missed her and wondered why the Prince suddenly ran off stage.

The Prince, in fact, does a lot of running and very little dancing. In the final - usually terribly dramatic -- moments, he is seen wrestling feebly with the armor-encased Von Rathbart until the latter runs off, followed by Odette, followed by the Prince.

Some time later, after the audience has been prepared for a water scene with billowing silk cloth and flickering lights, we see the two lovers gazing fondly at each other in the depths.

We have assumed than Von Rathbart is whisked away because he wears black, but there is none of the magic and manipulation that the Bolshoi conjures up with the role. . . . And I missed the bird costume.

Despite the changes, the company gives the ballet life. Its obvious enjoyment , youth, and energy shine through. The corps de ballet is well timed and together, and some of the individual dances were excellently executed.

In particular, the new pas de six in Act I (choreographed by Michael Pink) was charming. The dancing flowed and the dancers were well controlled, light, and fluffy.

But it was Galina Panova who gave the production class. Her Russian training shone through in her impeccable sense of timing, making each movement seem effortless and endless as one flowed into another.

Her arms, though not as ''boneless'' as Maya Plisetskaya's, undulated from shoulder to finger tip. Her ability to stop suddenly and hold an arabesque unsupported en pointe for moment after moment delighted the audience.

In the final moments of Act II, as she was being transformed back into a swan , her tremblings and her efforts to stay with Siegfried gave one goose (or perhaps swan) pimples.

As the black swan she was more of a nice showoff than an alluring schemer, and I felt she could have used her eyes, and sharper actions, much more to bewitch Siegfried. Instead, her dancing did the bewitching as she performed the familiar choreography with neatness, precision, and the lightness of swan's down.