Prom 51: Britten Sinfonia / Cleobury, Royal Albert Hall, London/Radio 3

Festival themes can enrich and embrace, but they can also impose. Whatever the theme, I would not have given programme space to Britten's worthless Young Apollo in this late Prom by the Britten Sinfonia under Nicholas Cleobury, and I wouldn't have wasted money booking the gifted Paul Lewis to play the piano part (which consists almost exclusively of scales and arpeggios). To do the master justice, he withdrew the work soon after its premiere in 1939. Let's accept his judgement.

In every other way this concert - too long though it was (by at least one Young Apollo unit) - made a big success of its central idea. Thea Musgrave's oboe concerto Helios, almost a decade old but not previously heard in London, proved a marvellous piece of concertante writing, full of energy and colour, and typical of its composer in its sheer geography, with wind players popping up on all sides to compare notes with the excellent main soloist, Nicholas Daniel.

The picture here is of the sun god in his chariot whipping his horses across the sky by day, then sailing home along the ocean stream in a large cup by night. We even got lighting effects to match. But the real beauty of the piece is its intense yet exuberant play of instrumental lines, bubbling with vitality, richly social, yet coherent and contained, like the best kind of chamber music. The players clearly enjoyed it hugely. What more can you ask?

John Woolrich's Double Mercury, commissioned for this concert (broadly for the orchestra of Stravinsky's Orpheus, which followed it on the programme), seemed more problematical in design, but was so full of dazzling ideas that it was hard to mind. The score says it lasts 20 minutes: I'm sure it was 30 in this (not always immaculate) performance. Behind it lies a series of episodes from Ovid, mutually unrelated but providing, Woolrich says, "ways of focusing the musical material".

The composer certainly has a flair for striking, lapidary sound images, and he has a precise ear. The wind scoring in Double Mercury is both daring and utterly convincing, even when it stretches the players to their limits. And there is never any over-scoring; the ideas inhabit their own space, and across them flow long musical lines which transport them, often at high speed, from A to Z (wherever that may be).

It's a high-risk piece of work, and occasionally one feels Woolrich is so high on the risk that he can't quite bring himself to stop. That, admittedly, is a defect with a distinguished ancestry; and perhaps time will show that it isn't a defect at all.