Cawston was born in Wantage in 1911, and was educated at Lancing College. He matriculated at Pembroke College in 1930. During his time at the College, Cawston was on the Athletics team. In 1932 he became Secretary, and in 1933 he became Captain of the College Athletics Club. He received a Blue for Athletics in 1931 when competing in and winning the Low Hurdles. Cawston also played cricket, and having previously played for Sussex County, he also played for the University, and was awarded a Blue in 1932. After finishing his degree in 1933, he continued his cricket career with the Egyptian national team. After retiring from cricket, he became a headmaster. Cawston died in 1998.