Prom 3: King Priam, Royal Albert Hall, London

First staged in 1962, Michael Tippett's second opera, King Priam, was an attempt to reanimate mythological material in the form of a modern opera seria with Brechtian devices and much posing of questions about choice and fate. To set his own Homer-based libretto, Tippett felt it necessary to jettison virtually all the attractions of his earlier music - the long lyrical melodies, exuberant contrapuntal cross rhythms and richly figured textures - for an idiom of stark gestures, abrupt contrasts and grinding superimpositions, with the orchestra broken down into small ensembles and hardly ever heard all together.

When it works, as in the brazen opening music which returns so cathartically at the end, or in the interruption of the Trojan rejoicings over the death of Patroclus by Achilles's terrifying war cry, the dramatic effect is overwhelming. But elsewhere, imparting a sense of continuity and drive to the continual shufflings of jagged lines and thinly scored sections depends to a perilous extent on the conductor. What a shame, then, that in bringing the work to the BBC Proms for the first time, David Atherton chose to compound the problems with his own tinkerings.

One of Tippett's ideas was to identify each character with specific instruments: so the voice of proud Hecuba is meant to ride on a surging single line for all the violins, and Andromache to keen over a monody for all the cellos. Parts of these lines are notoriously tricky, but can be negotiated -as Kent Opera triumphantly showed under Roger Norrington. There seems little excuse these days, except to save a bit of rehearsal time, for Atherton's transference of tracts of string writing to solo instruments - which then had to be amplified to fill the vastness of the Royal Albert Hall - and this recourse flattened dynamics and punched holes in the continuity, especially in the long, string-based scene opening Act III.

The pity of it all was that Atherton otherwise understands the work so well and had here about as fine a British cast as could be assembled, with David Wilson-Johnson quite magnificently articulate as Priam, whom Tippett - unlike Homer - makes his central character. Susan Bickley was particularly fine as Andromache, William Dazeley stentorian as Hector and Martyn Hill as Achilles touching in that moment of guitar-accompanied calm that Tippett inserts so tellingly into the brazen war music of Act II - enthusiastically rampaged through by the BBC Singers and National Orchestra of Wales.

A qualified success then in a work which is, itself, balanced on a knife edge. But it might have been stronger had Tippett's original requirements been realised to the full.