When Knocker was born her father was patrolling the coast of West Africa as commander of the gun vessel HMS Fly.

[1] In 1913 Knocker was invited to be an assistant to Leopold Auer at the Saint Petersburg Conservatory, but had to return to England on the outbreak of World War I in 1914.

Pupils included Leah Willoughby, Gerald Finzi, Phyllis Ebsworth, Basil Cameron, Jean Stewart, Mary Ibberson and Sybil Eaton.

When Mary Ibberson set up the first Rural Music School, based in Hitchin, in 1929, Knocker was a member of the advisory board.

In 1932 The Times published a letter from Knocker and her friend Edith Croll with the title "Good violins lying idle".