The original prototype was designed by SOE motor cycle enthusiast Harry Lester, from an idea developed by * Lt. Colonel John Dolphin, the Commanding Officer of Station IX, the secret Inter-Services Military Research Establishment based in a mansion an hours drive north of London near the town of Welwyn in Hertfordshire, which had been taken over for the war effort. Powered by a Villiers 98 cm3 single-cylinder two-stroke petrol (gasoline) engine, the Welbike was designed to fit into a standard parachute airdrop container 51 inches (130 cm), 15 inches (38 cm) high and 12 inches (30 cm) inches wide and be easily assembled and ready for use as quickly as possible. The name Welbike comes from the custom that all the clandestine equipment devised at Station IX in Welwyn had names starting with Wel, e.g, Welman, Welrod. There was very limited space in the airborne equipment container, so the Welbike had no suspension, no lights and just a single rear brake.
The fuel tank was as small as possible and had to be pressurised by a pump[clarification needed] as it was too small for gravity feed. The range on maximum capacity of 6.5 pints of fuel was a respectable 90 miles at about 30 mph. To save time the tanks were pressurised before the Welbike went into action. The Welbike was then packed into the parachute container with the rear wheel to the base of the parachute canister, which had a percussion head to minimise damage on landing. Once it hit the ground all that was needed was to twist the handlebars into position and lock them on spring-loaded pins. The saddle was pulled up and the footrests folded out ready to push start the two stroke engine and ride into action. The aim was that a paratrooper could remove the Welbike from its special green container (which was marked in white lettering with the words Motor Cycle) and its easily identified coloured parachute, and be on the road within 11 seconds. The prototype survived extensive drop testing at the Special Operations School at Arisaig in Scotland where it was demonstrated to the commando forces.
The prototype was then sent to the Excelsior Ltd for further development. A number of pre-production machines were built for further testing and experimental modifications at the Airborne Forces Experimental Establishment at Sherburn-in-Elmet near Leeds in September 1942, including dropping them from aircraft to land by parachute. The Villers engine was found to be seriously under powered when ridden by a fully equipped soldier, so it was retuned for maximum power.
The simple design of the Welbike meant that it was easy and quick to produce and from 1942 went into full production for issue to airborne forces for use in parachute assaults. By 1943 it was also being widely used by ground assault forces, including the Commandos and the Royal Marines particularly for beach landings at Anzio and Normandy. The small size of the Welbike meant that it also proved very useful as a general airfield transport by the Royal Air Force and aircrews based in the large Far East airfields would 'stow away' a Welbike if they could find one.
There were three production versions of the Welbike. The first 1,183 were known as the Mark 1 and were really the developed version of the original prototype with tuned engines. These can be easily identified as they did not have a rear mudguard fitted. One thousand four hundred Mark 2 Series 1 Welbikes were produced and these had a range of minor modifications, including the addition of the rear mudguard. The final batch of 1,340 was the Mark 2 Series 2 and had 'saddle' fuel tanks with a splash shielding between them and an improved filler cap, as the original design required the removal of the pressurisation pump which was too time consuming.
In combat situations, however, the Welbike could prove a liability as paratroops needed to get under cover as quickly as possible and had to find the Welbike containers before they could even start to assemble them. The difference in weight between a parachutist and a container meant that they often landed some distance apart, rather defeating the object, and many were captured by enemy forces or lost before they could even be used. The low power and small wheels also meant that they struggled to cope adequately with the often rough battlefield roads so were often abandoned by troops who found it easier to continue on foot. Another problem for the Welbike was that by the time it was in mass production much larger gliders had been developed that could carry bigger and more powerful motorcycles such as the Royal Enfield