Petroc Trelawny visits St Paul's Girls School in Hammersmith, West London, where Holst taught music from 1905 until his retirement in 1934.
In his music room overlooking Brook Green, the composer wrote some of his most famous works, including The Planets and Brook Green suites.
The school still reveres its eccentric teacher as recent music students testify and one of Holst's own pupils, Margaret Eliot, recalls what Holst was like as a teacher and a man.
And there is revealing archive from Holst's composer-colleagues and friends, Ralph Vaughan Williams and Herbert Howells, as well as from Holst's late daughter, Imogen.
Petroc Trelawny visits St Paul's Girls School in West London, where Holst taught.