A few composers have been locked up: Schubert (bad language to the police), Beethoven (arrested on suspicion of vagrancy), but only one woman has done time, and that for an excellent cause: the magnificently one-off Dame Ethel Smyth.

Dame Ethel Smyth

Tweedy, opinionated, passionate, and, in those days an unfashionable connoisseur of Australian reds, she was rarely seen without a tam ‘o shanter and an English sheepdog – she had six, all called Pan. Smyth never did anything by halves. In the words of Edward Sackville-West, “she only had to see an empty basket, and in went all the eggs.”

It was in 1910 that she joined the Women’s Social and Political Union, mostly on principle, but also partly on account of a newly developed romantic enthusiasm for its charismatic leader Emmeline Pankhurst. “Her personality and style of speaking swept me off my feet at once,” wrote Smyth. “I knew that before long I should become her slave.”

Pledging to forswear music for two years, she did however bend that rule in order to compose the immensely popular and incredibly catchy The March of the Women. Premiered at the Royal Albert Hall, Smyth drilled...