Walton's music for Olivier's Henry V is considered one of the finest film scores. When he composed it in 1943-44, he was already an experienced exponent of the genre, with the Spitfire Prelude and Fugue in The First of the Few to his credit; he went on to score with equal brilliance Olivier's other Shakespearean films, Hamlet and Richard III.

Curiously, Walton himself arranged just two short extracts from Henry V for the concert hall, though various larger suites were adapted by other hands. This new version, premiered alongside a screening of the film as part of the Brighton festival, was more ambitious, comprising a live performance of the entire score, played by the Royal Philharmonic Orchestra, with the Brighton Festival Chorus and Youth Choir under Carl Davis. The score was reconstructed by Dominic Sewell: parts of Walton's manuscript had, sadly, gone missing. Where sections were lost, Sewell transcribed them directly from the original soundtrack.

The resulting performance was not without its problems. Questions of the sound balance between film and live music had not all been solved, with the volume level of the dialogue booming out coarsely into the auditorium, and there were occasional lapses in synchronisation.

But nothing could disguise the immense contribution Walton's music makes to scene after scene, bringing a sense of scale and grandeur to the stylised sets. Most miraculous of all is the battle sequence, where the scoring brings a feeling of physicality to the charge that lifts the listener up on to the screen itself. After this, half the audience would have gone off to invade France, had there been a boat ready at the end of Brighton Pier.