John Cavanagh was born in 1914 in Irland.
In the 30's, he went to Paris and joined the house of Edward Molyneux until World War II began when he returned to Ireland.
After the war, he returned to Paris and joined Pierre Balmain from 1947 to 1951.
He returned to London and in 1952 opened his own house there. His success continued throughout the 60's with the production of wholesale and ready-to-wear lines. His clothes had an international appeal as well as understanding the traditions of British life. He noted "a couturier worth his name must design in the world-stream of design change, but direct it to the lives of his clients that make this business exist."
In 1964, he said "Couture will and must continue, it is the lifeblood of the ready-to-wear".
Cavanagh is a member of the Incorporated Society of London Fashion Designers, along with other leading British designers.
He designed the wedding dresses for both the Duchess of Kent and Princess Alexandra.
He retired in 1974.
Cavanagh was successful from the start. He approached his work as a couturier with a keen eye for cut and line. He promoted full-skirted, round shouldered looks as effectively as lean, long lines. His 50's designs anticipated the Sack or Chemise Dress which later became so popular.