In 1920, Eileen Armstrong enjoyed the most successful year of her career when she won the silver medal in the high diving event at the Antwerpen Olympics. She also won the National High Diving Championship that year, and was second to Belle White in the National Graceful (Plain) Diving Championship. Armstrong retained her national high diving title in 1921 and in 1924, after finishing second to White again in the plain diving championship, was selected for her second Olympics, but failed to reach the final in Paris. Armstrong returned to form in 1927 and was again the national plain diving runner-up to White. After finishing second and third respectively in the two-day trial for the 1928 Olympics, it seemed certain Armstrong would be going to her third Games but was a surprise omission. In 1972, at the age of 78, Armstrong married her husband James Purdy.
Great Britain