The Excelsior Motor Company of Great Britain designed a lightweight motorized cycle based on their experience building scooters and motorcycles before the war.
The work was done in cooperation with SOE (Special Operations Excecutive) at Station IX, Welwyn, which is how the scooter got it's name. All machines developed there were given names with the prefix "Wel" such as the Welcar, Welboat and Welsub, etc.