The son of a Scottish-born doctor, Jack Robertson was one of three brothers who competed at the Olympics. Jack took part in the tandem cycling event at Paris in 1900 while his younger brothers David and Arthur both competed at the 1908 London Games at cycling and track athletics respectively. Jack started racing competitively in the early 1890s and in 1894 set a new one hour record of 26 miles 1670 yards (43 km) at Herne Hill. He also established NCU records for three, four, five, eight and nine miles, and all distances from11-26 miles. That same year he was second to Jack Green in the National 25-mile Track Championship. Robertson represented England in the professional one-mile and 100 km at 1895 World Championships in Cologne, and the following year won an international mile race at Olympia, ahead of F. Verbeyen of Germany. Originally the owner of a cycle business in Peterborough and Cambridge, Robertson moved on to become a motor car agent in London thanks to the advent of powered vehicles.