For its almost-farewell performance at the Kennedy Center, Britain's Royal Ballet yesterday afternoon danced "Swan Lake" with a cast from bottom to top that not only did itself proud in step execution, but was right as to type. The dancers so believed in what they were doing that those in the audience who might have welcomed a more varied repertoire this year couldn't but hope for the company's speedy return, even with the same classics.

Not only could academic dancing of high caliber be seen in the birthday waltzing and trip and in the ballroom quartet, but even the quadrille of swanlets, which easily becomes mechanical, had the rare quality of being on the verge of the great graceful movements of the swan corps.

Jennifer Penney, the Swan Queen, is the quintessentially English ballerina -- technically clean, clear in detail, and of delicate articulation. There's never a measure too much in this dancing. Hers is a cool, pure vision of the romantic ideal.

How can so upright a dancer do justice to the other part of the dual role, that of the Swan Queen's impostor? Penney stressed the impostor's pride, an aspect of evil.

Wayne Eagling, who has grown enormously in the classics since the company's Wolf Trap season two years ago, captured the dual aspects of his single role as the hero -- princely confidence and romantic confusion.

If there were dance highpoints they surely included Penney's and Eagling's lakeside adagios (especially Penney in Act 4), their Black Swan coda, Eagling's pensive solo before his adventures begin and Fiona Chadwick's variation in the ballroom quartet. But, so finely modulated at all levels was this performance that the dances of the original choreographers, Petipa and Ivanov, and contemporary Frederick Ashton, seemed almost of a piece.

In the Royal's goodbye of "Swan Lake" last night, Leslie Collier and Stephen Jefferies were scheduled to dance the leads.