[3] He established his first victory during an Easter Bank-Holiday BARC Open Meeting on 28 March 1932, driving a supercharged Officine Meccaniche.
Over the next two years, he won three races in his Bugatti and broke the lap record for 2-litre cars at Snaefell Mountain Course on the Isle of Man, with an average speed of 72.15 mph (116.11 km/h).
[2] Because of health problems, Mathieson was unable to enter any races from 1934 to 1937, so his Bugatti was driven a few times by Chris Staniland.
[5] He entered the Grand Prix des Frontières on 9 June, but instead raced at the René le Bègue Cup held on the same day, finishing fifth.
[15] After 25 years of racing, Mathieson concentrated on his writing and his collection of photographs, together with his wife Mila Parély, a French actress he had married in 1947.