Jim ( or Jimmy ) Clark OBE ( 4 March 1936 -- 7 April 1968 ) was a British Formula One racing driver from Scotland . James `` Jim '' ( or `` Jimmy '' ) Clark , Jr. . OBE ( 4 March 1936 â `` 7 April 1968 ) was a British Formula One racing driver from Scotland , who won two World Championships , in 1963 and 1965 .