Sylvia, Royal Opera House, London

Bussell is still magnificent when she stays focused

Frederick Ashton's Sylvia is a ballet in which flesh-and-blood nymphs drink from painted streams, statues shoot silver arrows and gods regularly descend to sort out the plot. This Royal Ballet revival, commissioned for Ashton's centenary, is the first performance since the 1960s. It's full of steps, of sumptuous scene painting, but this isn't quite a lost classic. It's not until the third act that Sylvia steps beyond pastiche.

The ballet was choreographed in 1952, with a production that carefully evoked French 19th-century ballet, the period of Delibes's pretty 1876 score. The designs, by Robin and Christopher Ironside, are splendidly full of perspective-painted forests and temples, sailing boats and Greek key pattern.

The plot is remarkably silly: the shepherd Aminta loves the huntress Sylvia, who rejects him until the god Eros shoots her with the arrow of love. Then she gets abducted by the wicked hunter Orion, rescued by Eros, rebuked by the goddess Diana and finally reunited with her beloved.

Ashton kept tinkering with Sylvia, finally cutting the ballet down to a single act. Christopher Newton's production returns to the original three acts, with steps recovered from film and dancers' memories. It's a confident reconstruction, and strongly danced. The footwork is brilliant, hugely demanding; even attendants whip through fouettés and dashing shifts of direction. The ballerina has everything from hops on pointe to hair-raising fish dives. Darcey Bussell, in her first full-length role after maternity leave, sails over technical hurdles. Her feet are strong and beautifully articulated, her line bold, her jump magnificent. Yet her Sylvia goes in and out of focus. She'll bourrée forwards with expansive grace, then lose the precision needed to clinch a phrase. If Bussell stops short of complete authority, so does the choreography. Sylvia is unmistakably Ashtonian - as "new" 19th-century ballet goes, this is infinitely better than tosh like the Bolshoi's Pharaoh's Daughter - but it's not until the last act that it becomes distinctive. Sylvia's last-act solo is dazzling, Ashton turning fiendish footwork into stylish wit. The duet for Sylvia and Aminta combines fireworks and tenderness: she soars dramatically into his arms, and he draws her back to touch her cheek.

Jonathan Cope is a touching Aminta, phrasing dance and (often dotty) mime with graceful attention. Thiago Soares is an exuberant Orion, jumping and snarling with gusto. This Sylvia is lovingly restored, brightly danced.