Berkeley first detected symptoms of the disease in June 2005 and was diagnosed soon after. "Playing the piano became painful and even clumsier than usual," he writes. "Not just wrong notes, but unintended discords as I hit two or three keys per finger."

In attempting to live with the disease, he adds, he adopted "a rather Buddhist approach to life," and as a result, has been writing "some of the most direct and uncluttered music I have composed."

Recently, Berkeley says, he has regained much of his strength by swimming, but recovery has been slow.

Berkeley is the son of composer Lennox Berkeley and the godson of Benjamin Britten. His many works includes the operas Baa Baa Black Sheep and Jane Eyre, the orchestral piece Secret Garden, and a Concerto for Orchestra, which was premiered by BBC National Orchestra of Wales at the Proms in 2005.