Ron Stedman attended Beckenham and Penge Grammar School, before being conscripted into the Army in 1946. During his time in service, he broke the 100 yard record at the Army Swimming Championships in both 1946 and 1947, and the 220 record in the second of those years. Stedman was selected for the 1947 European Championships at Monte Carlo, and the following year won the first of two consecutive national 100 yard titles. He also competed at the London Olympics that year, and went on to reach the 100 metres semi-final. In addition to his 1948 and 1949 national 100 titles, Stedman was third in 1950, and second in 1951. He continued swimming two or three times a week well beyond the age of 80.