Four suicide bombers killed 52 and injured more than 700 people on London public transport in 2005
Most 7/7 victims who were not killed instantly, but subsequently died, had blast wounds so severe they probably would not have lived even with medical treatment, the inquests have been told.
Experts found that of 18 people thought to have lived for some time after the blasts, most had "unsurvivable" wounds.
The inquests are currently hearing about the 13 people killed in the bus bombing in Tavistock Square, in 2005.
They were also told of "unacceptable" delays in getting medics to the scene.
Four suicide bombers targeted three Tube trains - at Aldgate, Edgware Road and Russell Square - as well as the number 30 bus, killing a total of 52 passengers.
Colonel Peter Mahoney, who is defence professor of anaesthesia and critical care at the Royal Centre for Defence Medicine in Birmingham, led a team that investigated what happened to 18 victims thought to have lived for some time after the explosions.
They concluded, on the balance of probabilities, that 15 of them were so badly injured that normal medical treatment could not have saved them.
The evidence was not clear enough for them to come to firm conclusions in the cases of the other three.
The team said that the injuries sustained in the blasts were probably unsurvivable for Richard Ellery, 21, Fiona Stevenson, 29, Carrie Taylor, 24, Michael Stanley Brewster, 52, Laura Webb, 29, Anna Brandt, 42, Ojara Ikeagwu, 55, Behnaz Mozakka, 47, Christian Small, 28, Mala Trivedi, 51, Marie Hartley, 34, Shahara Islam, 20, Miriam Hyman, 31, William Wise, 54, and Gladys Wundowa, 50.
However they were unable to form a clear view as to whether the wounds suffered by Samantha Badham, 35, Philip Beer, 22, and Shelley Mather, 26, were unlikely to be survivable, he told the hearing at the Royal Courts of Justice in London.
Hugo Keith QC, counsel to the inquest, asked Col Mahoney if the military field hospital at Camp Bastion - the main British base in Helmand Province in southern Afghanistan - could cope with an attack on the scale of 7/7, which also left hundreds of people injured.
He replied: "If you presented us with the number of seriously injured people that happened in July 2005 in these bombings, and presented them all at once at our hospital in Bastion, there's no question that we would have struggled."
'Very poor'
Earlier on Monday the court heard details of delays in sending ambulances to help those injured in the bus bombing.
While the first paramedic crew arrived at the scene within minutes of the explosion, records show it was nearly an hour before more ambulances were sent to assist.
Hasib Hussain was the last of the four suicide bombers to detonate his device, at 0947 BST.
London Ambulance Service (LAS) received detailed calls about the incident within minutes of the blast, but senior LAS managers controlling the operation did not have access to this information in their command room and further ambulances were only sent to Tavistock Square at 1042 BST, the inquests were told.
Christopher Coltart, barrister for some of the bereaved families, asked ambulance operations manager Paul Gibson if he was prepared to accept that the "failure" of central ambulance control to dispatch ambulances to the scene for half an hour after it was made aware of the position was "totally unacceptable".
Marie Hartley was killed in the Tavistock Square bus bombing
Mr Gibson replied: "I can't explain the decisions that ambulance control made because I wasn't there at the time."
The court was also told that a member of the public called LAS at 0948 BST and said a bus had been blown up outside the British Medical Association, adding that there were "lots of people screaming".
Three minutes later a Metropolitan Police officer rang ambulance control and said 10 people had been injured in the blast.
But the LAS command team had gone into a special "gold suite" used for major incidents, which at the time did not give them access to the system recording these messages.
One paramedic said ambulance control told her to stand by at Fulham ambulance station in west London. She and her colleagues waited there, listening to radio news reports, until they were deployed at 1042 BST.
Mr Gibson said; "From my perspective of managing the scene, we didn't have a delay in receiving vehicles."
Another ambulance crew radioed in to control at 1052 BST to say they had been sent to Kentish Town in north London but there was no incident there.
Mr Coltart asked Mr Gibson: "Is this not absolutely symptomatic of what was happening that morning as a result of defective radios?"
Mr Gibson said there appeared to be a confusion of call signs, with two different vehicles being allocated the same call sign, and went on to concede there were "communication difficulties on the day".
The inquests at the Royal Courts of Justice in London, which began in October and are due to finish in March, were adjourned until Tuesday.
