Teams of plastic surgeons, eye surgeons, and orthopaedic specialists were immediately drafted in to treat multiple and complex wounds, each serious in itself.
It was the mixture of injuries that made the surgeons' job harder. Victims suffered burns, fractured bones, foreign bodies that had to be painstakingly removed, and also what are known as "blast" injuries - the impact of an explosion on the lungs and ears. Shrapnel pierces the skin and once through the surface shreds blood vessels, muscles, practically anything in its path.
St Thomas' Hospital said its longest operation on Friday night lasted 14 hours.
After stabilising victims' breathing and circulation, the fight to repair the body begins. Plastic surgeons were on hand to remove dead tissue and carry out skin grafts. Orthopaedic surgeons fixed metal pins in bones to stabilise limbs, and eye surgeons worked to remove pieces of glass and other debris.
Anthony Young, a consultant surgeon who was first on call on Friday at St Thomas', said: "Surviving the first 24 to 36 hours does not necessarily mean you will survive in the long term. There is always the danger of lungs filling up with fluid, as a lot of fluids must be given to burns victims. There is also always the risk of infection."
An accident and emergency consultant, Stephen Miles, from the Royal London Hospital, said: "It's a very difficult balancing act. The more fluid you give burns victims, the more chance there is of blood clotting. You can try to fix one thing, and cause detriment to another.
"First of all there is a fireball from an explosion, which causes intensive burns. Then there are bits thrown out by the bomb, fragments, and in this case nails. Limbs could instantly be blown away or the impact of a fragment causes dead tissue, which sometimes cannot be reconstituted and leads to amputation.
"In a way it's similar to land mine victims, where the metal and plastic go off under someone's legs and then rip the tissue to shreds as they move upwards."
He said it could take years for people to get over such a blast, "particularly the impact of burns injuries because skin grafts can be carried out over a long period of time."
Howard Baderman, an accident and emergency consultant at University College Hospital (UCH), said the episode was so "horrific" that hospital staff might need counselling to get over the trauma. All staff, from consultants to nurses, porters and telephonists, would be likely to suffer stress and strain in the coming days as the adrenalin left them, he added.
The families of the victims are also being comforted by nursing staff at UCH as they keep vigil at the hospital. "The families have been with the patients whenever that has been possible. They are not far away from them," said Mr Baderman.Reuse content