More than 750 St John Ambulance volunteers have offered to help at the new hospital set up to meet demand for intensive care beds as the coronavirus crisis escalates.
Up to 200 first aiders per day will help at the Nightingale Hospital set up in London's ExCel centre, which is usually used for exhibitions and trade fairs.
The volunteers will be needed day and night, with 100 on each shift.
The 143-year-old charity has around 8,500 regular volunteers and provides an auxiliary ambulance service - often at large public events.
The volunteers are currently going through selection and being given further training, and could be in the field caring for coronavirus patients as early as next Wednesday, the organisation said.
Many others will also be assisting in other makeshift centres set up in different parts of the country.
Alex Davies, 32, is one of the many St John Ambulance crew who answered the call for volunteers.
Mr Davies, who has 15 years experience with the organisation, has been appointed tactical commander of the St John volunteers at the Nightingale Hospital.
Mr Davies, who lives in Victoria in London, said dealing with death was often part of the job for ambulance crews, but would be harder for some of the other volunteers.
When asked about the scale of the Nightingale Hospital, he added:
Mr Davies, who is head of production engineering at a financial services company, has been granted indefinite leave to help at the Nightingale Hospital.
St John said it was in the midst of an unprecedented training push of more than 1,000 volunteers to ready them for frontline work alongside NHS staff as the pandemic deepens.
Ruth May, the NHS's chief nursing officer for England, said she was delighted at the charity's offer of help, adding: