The Russian conductor Valery Gergiev is no stranger to London musical life but his appearances have just acquired extra piquancy as he takes up the post of Principal Conductor with the London Symphony Orchestra. A complete cycle of Mahler's symphonies may not be the most original calling card, but it makes its point: "No matter how big the project," Gergiev is saying, "I can handle it."

He opened the series with Mahler's Third, 95 minutes of unbridled musical gigantism: the contrasts in the opening movement alone are sufficient for a whole symphony. As Gergiev set things in motion at a slow, deliberate pace, the sheer weight of the orchestral sound was an immediate shock. The LSO is an orchestra of gifted soloists, and as the symphony progressed, individual players came into their own, responding to Gergiev's fluttering fingers as if they were throwing bolts of electricity.

Gergiev enjoyed casting tiny details in a garish light, and brief moments of silence carried as much drama as the most agitated passages. If there was sometimes disjointed feeling, the music seemed to demand it. The third movement capered infectiously, and there was a mellow humour in the off-stage flugelhorn solos. Swedish alto Anna Larsson was the vocal soloist, her brief song seeming to carry all the sadness in the world. The contrast with the bright timbres of the Tiffin Boys' Choir could not have been starker, and Gergiev seemed to be humming along: at times he is a distracting presence.

Some ragged ensemble in the final movement hardly mattered as the music wound towards catharsis. A few moments of silence to catch our breath would not have gone amiss, but the audience was impatient to register its approval. For now, at least, Gergiev can do no wrong.