There are plenty of reasons to be depressed about the state of musical education in Britain today. But to witness a London Schools Symphony Orchestra event is to realise that all is not lost. This is an organisation able to take schoolchildren of Grade 7 and above and mould them over an intensive few days into an ensemble of the highest calibre.

The intake for this holiday’s session, which contained an impressive female bias, not least in the brass department, was coached by the mildly eccentric Finnish conductor Leif Segerstam in a programme of music by Sibelius and himself. The orchestra took a little while to get into its stride, and the opening Seventh Symphony of Sibelius was a brave attempt at the composer’s laconic masterpiece rather than a polished or wholly convincing account.

With the arrival on the platform of the young Finnish soloist Elina Vähälä, however, for Sibelius’s Violin Concerto, the orchestra slid into top gear. Vähälä has star quality, exuding confidence and bowing with a natural physical grace that puts one in mind of Anne-Sophie Mutter. She also has an enviable variety of articulation as well as a tonal depth enhanced by the 1678 Stradivarius she plays.

For the mysterious opening of the concerto, Segerstam produced an atmospheric whispering tremolo. Similarly, in the slow movement the soloist was provided with a soft cushion of sotto voce horns and susurrating pizzicato cellos over which to rhapsodise.

Segerstam is not only a conductor but also a composer, and a prolific one at that. Having started to write symphonies at the age of five, he seems unable to stop. Last night, his Symphony No 189 (Marimekko) was heard for the first time but even before its premiere he had upped his total to 215.

The secret behind this one-man symphony factory is that he has developed a system: the conductor is dispensed with while the players are given the liberty to roam rhythmically, coming together at climactic “now moments”. Rising to the challenge, the young players brilliantly demonstrated both the improvisatory flair and the communal discipline required.