Born on 12 March 1936 at Sutton Coldfield, Warwickshire to confectioner's agent Arthur Willcox (1891-1967) and Helen Patience (1905-1971), née Davies, she had a wealthy background.

She rode in her first three-day event with partner High and Mighty, an Arabian/pony cross, in 1955 at the young age of eighteen.

After a few more years Willcox won the event with High and Mighty in 1957, leading the competition start to finish.

Willcox also competed in the 1957 European Championships with High and Mighty, earning both team and individual gold medals.

However, a fall in 1971 at the Tidworth Horse Trials left her partially paralyzed, and she gave up eventing and focused on dressage.