Mr. Ashton and I may make bad ballets, but we never make incompetent ballets."" So says Balanchine, and here are his British counterpart's 50 years of bad, good, and indifferent choreography--reverently chronicled and satisfactorily illustrated with some 250 black-and-white rehearsal and performance photos. As the Vic-Wells Ballet became the Sadler's Wells Ballet and then the Royal Ballet, Sir Fred became the national institution who embodies British dance, complete with a trademark ""Fred step."" And his noted colleagues--presences like the Sitwells and Marie Rambert, composers like Britten and Constant Lambert, designers like Beaton, dancers like Markova and Fonteyn--figure prominently as Vaughan recreates the genesis and analyzes the finished form of each piece. The choreographer's spoken words (three years of interviews) and scribbled notes add some immediacy, and a 50-page chronology lists everybody involved with every dance. There may be no trace of backstage blood, sweat, or venom in these pages, but there is detail in vast repose for insatiable balletomanes and Fonteyn and others in flight for all those who warm to the arcs and sways that are British ballet.