One member of staff at the hospital said: "Most people are very tired after a gruelling two days."
The hospital was still treating 14 patients from the blast, including two in a critical condition, out of the 38 casualties who had been taken to accident and emergency on Thursday.
Among those admitted to the hospital was a woman identified simply as Davinia, who was pictured in newspapers with her face covered by a surgical mask to protect her burns.
A hospital spokesman said: "She was treated at St Mary's. She's no longer here."
Insiders at the hospital said that after the initial alert, when "vast numbers of staff" were summoned to attend via text message, the situation returned to normal. Patients were moved from accident and emergency, which coped with the initial wave of casualties, or were discharged.
Those with serious injuries were moved to intensive care, while those with fractures were transferred to wards.
Three patients were transferred to the Chelsea and Westminster Hospital, where the main specialist burns unit for London is, while those with minor injuries were discharged. Other injuries included loss of limbs, damage from smoke inhalation, burns and lacerations.
Professor John Henry, the recently retired head of accident and emergency at St Mary's, said the hospital had been well prepared for such a catastrophe.
He said: "This is a tribute to our preparedness. We have been working on it for three years. We have good systems in place and they worked."
The timing of the explosion meant that accident and emergency was not busy and there was a full contingent of staff, making the response easier.
A hospital worker told the Prince of Wales, who visited St Mary's on Friday with the Duchess of Cornwall, that the hospital had been "inundated" with people offering to work.
Andrew Meyer, a hospital worker, told Prince Charles: "Eleven years of service, I've never had a day like it. The training kicked in for everyone.
"The patients that were alive were so brave... not screaming. They waited their turn."
On the day of the explosion, some existing patients had been discharged to free up about 30 beds, while routine operations were cancelled.
St Mary's, which specialises in acute services such as emergency care, is no stranger to large-scale disasters. The hospital's major incident plan was last put into practice when it treated victims of the Paddington rail crash.
Security at the hospital remains tight. Even the relatives of patients had trouble gaining access. Jonathan Randall, 22, went to St Mary's yesterday to visit his brother Chris, 28, who was being treated for burns.
Mr Randall said: "I was there all day on Thursday. The staff were brilliant. It was quite manic. From a security point of view, it was quite difficult to get in there."
He said: "Once you got used to people with burns, it was strangely relaxed, because everyone was there for so long and people were in shock. Everyone had at least one family member in and they were talking to them. They were just exhausted."
The other key hospitals
Situated near Russell Square, where a bomb ripped through a bus. It treated 61 casualties, including one adult who was transferred from Great Ormond Street. Of these, 23 were still being treated yesterday afternoon, including five in intensive care. Injuries included wounds caused by stone, glass, metal or other debris. The majority of patients, about 50, were treated for minor injuries.
The hospital, near Liverpool Street station, was still treating 26 victims yesterday and seven remained in intensive care. A total of 183 patients were brought in from two of the explosions. Eight victims were critically injured, including one in cardiac arrest and six people were operated on. Senior consultant Laurence Gant said: "The hospital was fully staffed last night. All staff due on duty made their way into work despite transport difficulties."
ROYAL FREE, HAMPSTEAD
Of the 13 patients initially admitted, eight were still being treated yesterday afternoon. Four had been discharged, and one transferred to Guy's and St Thomas's. Routine operations and staffing levels were back to normal yesterday. There were no deaths and only one child was treated, for minor injuries.
GUY'S AND ST THOMAS'S
The hospital trust was treating 13 patients last night, including 11 of the original 21 patients who had been admitted on Thursday, as well as two more patients who were admitted yesterday for specialist treatment. One of the remaining patients was in a critical, but stable, condition, while the others were all in stable conditions. Six people underwent surgery yesterday.
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