John Duncan Cleworth (born 20 April 1957) is a male British former swimmer.
Cleworth is a relative of Addin Tyldesley,[1] who competed in the men's 100 metre freestyle event at the 1908 Summer Olympics. Duncan's ancestors were said to be a famous swimming family.[1] Like his family members, he swam at the Tyldesley Swimming and Water Polo Club, where he was later declared one of their most famous members.[2]