The finishing touches are being put on the NHS Nightingale Hospital which is set to play a key role in the war against coroanvirus.
More than 16,000 members of staff will be needed to run the facility, in east London, when it reaches full capacity and members of the army have been working 15-hour days so it is finished as soon as possible.
It will have beds for 4,000 coronavirus patients, make it the largest critical care facility in the world according to reports, and will mostly treat younger sufferers.
The temporary hospital, built inside the ExCel convention centre in east London, is due to be finished later today despite building work starting only last Wednesday.
And members of the British Army who helped have compared the war against coronavirus to the Battle of the Somme more than 100 years ago.
Colonel Ashleigh Boreham, who has carried out two tours of Iraq and one of Afghanistan, said it was the biggest mission of his career.
Colonel Boreham, who has helped create field hospitals around the world, said: "We are building a hospital for people in our nation. You are saving people's lives and they could be the lives of your families. It's the biggest job I've ever done.
"My grandfather was at the Somme, this is no different. I'm just at a different battle.
"I'm from London, I have friends and family in London.
"Many of the people working here, many of the soldiers working here, are from London.
"We are doing this to save the lives of Londoners. These are our comrades, there's no difference. It doesn't matter if they are civilian or military."
The facility will be used to treat Covid-19 patients who have been transferred from other intensive care units (ICU) across London.
The Nightingale will become one of the biggest hospitals in the world, according to its chief operating officer Natalie Forrest.
Speaking to visiting reporters, Ms Forrest said a "scary" number of staff would be needed to run the facility at full capacity and appealed for volunteers to come forward.
"If we have to use this facility, which I really hope we don't because everyone is staying home and washing their hands and social distancing, we will need thousands of doctors and nurses and volunteers to run this facility," she said.
Asked to clarify how many are required, Ms Forrest said: "The numbers are scary, but if I tell you that to run one ward, including all of our ancillary staff, we need 200 members of staff."
The hospital will initially aim to care for 42 patients, before its expansion is "ramped up" to ensure it can meet its full 4,000-bed capacity in two weeks' time if needed, the Nightingale's chief medical director Alan McGlennan said.
He said coronavirus patients who are transferred to the hospital will already be on a ventilator and will remain at the Nightingale until their course of ventilation is finished.
Coronavirus patients suffering from other serious conditions - such as cardiac issues - will be better cared for at other specialist centres, Mr McGlennan said.
While the Nightingale will be able to provide up to 4,000 ventilator beds if they are needed, NHS London will still have control over the "most precious resources", he added.
Eamonn Sullivan, the hospital's director of nursing, said the facility will be able to operate as a large intensive care unit or a normal ward, depending on demand.
The Nightingale will also include support services found in other NHS hospitals, such as pharmacies and therapy treatment, Mr Sullivan said.
Meanwhile, staff working at the Nightingale will be able to sleep at nearby hotels once they finish their shift, Mr Sullivan said.
"We have got the facility here at ExCel and there is many, many thousands of hotel rooms. It is a perfect location," he said.
"If staff wanted to stay, they could stay, so it is optional. But if they want to go home, then they can."
An NHS England spokesman said the equipment being used at the Nightingale was all "new kit" and had not been borrowed from other hospitals.
Military personnel have been working 15-hour shifts to help build the hospital.
Colonel Boreham, from the Army Medical Services, said plans for the hospital were only conceived on March 21 in a meeting between the NHS and military.
Since then, up to 200 personnel, including infantry from the 1st Battalion The Royal Anglian Regiment, have been assisting contractors and NHS staff with its construction.
Col Boreham, who is the project's senior military lead, supporting the advisory mentoring team, told the PA news agency: "I arrived on site and met with the NHS last Saturday.
"We literally sat down with a piece of paper and some drawings and came up with a concept that the NHS and us thought would work well.
"From that point there, we have re-purposed this wonderful building into an NHS hospital."
He said the number of military personnel on site has expanded from eight to 60 over the past week, ranging from medical advisers, engineers and logistics staff.
However, the numbers increased further when infantry soldiers were brought in to help at the peak of the facility's construction.
"It's long hours," Col Boreham said on Tuesday.
"It's like what they would normally do on operations.
"It's longer hours than what people are used to working in some parts of the organisation.
"We start at about 7am in the morning and will finish at 10pm at night and we have been here since the start."
Col Boreham said all military staff were on a rotation system to ensure they are given time to rest and recuperate.
He said the ExCel centre was chosen by the NHS, but supported by military planners due to its existing utilities.
"This site is perfect," he said.
"It has a corridor down the middle, it has got big areas to create wards and bays and sufficient utilities to sustain a facility of this size."
