The club was formed on McIndoe's in

The club was formed on McIndoe's initiative in June 1941 with 39 patients, primarily as a drinking club. The members were aircrew patients in the hospital and the surgeons and anaesthetists who treated them. Aircrew members had to be serving airmen who had gone through at least two surgical procedures. By the end of the war the club had 649 members.[1]

The name "Guinea Pig" – the rodent species commonly used as a laboratory test subject – was chosen to reflect the experimental nature of the techniques and equipment used for reconstructive work carried out at East Grinstead. The treatment of burns by surgery was in its infancy, and many casualties were suffering from injuries which, only a few years earlier, would have led to certain death. The original members were Royal Air Force (RAF) aircrew who had severe burns, generally to the face or hands. Most were British but other significant minorities included Canadians, Australians, New Zealanders and by the end of the war Americans, French, Russians, Czechs and Poles. During the Battle of Britain, most of the patients were fighter pilots, but by the end of the war around 80% of the members were from bomber crews of RAF Bomber Command.

Before the war the RAF had made preparations by setting up burns units in several hospitals to treat the expected casualties. At East Grinstead, McIndoe and his colleagues, including Albert Ross Tilley, developed and improved many techniques for treating and reconstructing burns victims. They had to deal with very severe injuries: one man, Air Gunner Les Wilkins, lost his face and hands and McIndoe recreated his fingers by making incisions between his knuckles.

Aware that many patients would have to stay in hospital for several years and undergo many reconstructive operations, MacIndoe set out to make their lives relaxed and socially productive. He gave much thought to the reintegration of patients into normal life after treatment, an aspect of care that had previously been neglected. They were encouraged to lead as normal a life as possible, including being permitted to wear their own clothes or service uniforms instead of "convalescent blues", and to leave the hospital at will. Local families were encouraged to welcome them as guests, and other residents to treat them without distinction: East Grinstead became "the town that did not stare". The Guinea Pig Club was part of these efforts to make life in hospital easier, and to rebuild patients psychologically in preparation for life outside. There were even barrels of beer in wards to encourage an informal and happy atmosphere.

Later, many of the men also served in other capacities in RAF operations control rooms, and occasionally as pilots between the surgeries. Those unable to serve in any capacity received full pay until the last surgical operations and only then were invalided out of the service. McIndoe also later loaned some of his patients money for their subsequent entry into civilian life.