The commentary on this film is by perhaps the most famous motorcycle racing rider of the day, Geoff Duke, known as The Duke -- making him an ideal commentator, especially for the Scarborough Road Races.
By the time that this film was made in 1955 Duke had won six World Championship races at 350cc and 500cc, starting out with Norton in 1950 before switching to the Italian Gilera in 1953 (and then back again to Norton in 1958). 1955 was in fact the last year he was to win a World Championship.