Prom 25 Royal Albert Hall, London

Whether it was the Disney connection that brought them in I can't say, but when Lawrence Foster cued The Sorcerer's Apprentice at Tuesday night's Prom, he had a full house. Russia's flamboyant Evgeny Svetlanov had originally been booked for the gig, but Foster's patiently paced performance scored highest for clear articulation and a low-key sense of narrative. It was conscientious and just a tad dull.

But this Sorcerer wasn't for quitting. Halfway through the first movement of Tchaikovsky's Violin Concerto, one of Vadim Repin's strings suddenly snapped. After momentarily faltering, he stopped, looked at his instrument, politely turned down the offer of the leader's violin, took a spare string out of his top pocket and proceeded to put things to rights. Of course, this was just the sort of thing that promenaders – and journalists – pray for. Foster took out a handkerchief and mopped Repin's brow, and as the violinist retuned, he told the story of how another fiddler broke a string towards the end of Penderecki's 40-minute Violin Concerto and insisted on starting from scratch.

Not here, however, where a very decisive "from measure 127" got things moving. And so off we went again, picking up what had already established itself as a genuine class act. Repin is the finest violinist of his generation – and I'm not forgetting his fellow-Zakhar Bron pupil, Maxim Vengerov. He has it all: a facilitating technique, a shimmering tone, an individual personality and bags to say about the music. OK, after the "break" he played some fairly OTT tricks to the gallery, but they all worked, and the finale was breathtaking.

If you'd have veiled the broadcast with a sheet of shellac surface noise, you would never have doubted the presence of a top-grade old-world fiddler. And just to prove the point, Repin coaxed the BBC Symphony strings into plucking a delicate accompaniment for some startling variations on Carnival in Venice. He'd make his fiddle sing, chuckle, spit or glide, always without the least visible effort.

It was quite an evening for dramatic incident. My usual interval stroll past the Albert Memorial was interrupted by a burly film-hand who waved me off the cycle path as what looked like a motley A-Team (motorbike plus a hefty four-wheel drive) prepared to roar from one end of the park to the other. A nearby assistant confided the facts: a Radio 3 trail. Some image change!

Meanwhile, back at the Hall, Foster and the orchestra prepared for a fairly nondescript second half. Ravel's Pavane for a Dead Infanta sagged under the weight of excessive feeling. There was too much wringing of hands, not enough grace, while Mussorgsky's Pictures at an Exhibition, served in Ravel's ubiquitous orchestration, had to suffer some conspicuously inconsistent playing from the BBC brass. Odd movements worked quite well – a nicely turned sax in "The Old Castle" and some crisp percussion in "Baba Yaga". But it was a workaday Pictures, ultimately forgettable. A good job we'd already stored more than enough memories to be getting on with.

This Prom will be rebroadcast today on Radio 3 at 2pm.