A firefighter called to the 7/7 terror attacks told an inquest how "protocol" forced his team to stand by and watch as horrifically injured passengers emerged from one of the bombed trains.
Andrew Shaw was among the first to arrive at King's Cross Tube station after Jermaine Lindsay blew himself up on a Piccadilly line train.
But though desperate to head into the smoke-filled tunnel where passengers lay dying, his senior officer insisted he wait for a back-up crew.
This did not come until 9.42 - nearly an hour after the initial explosion and after it was mistakenly directed to the wrong location.
The inquest heard how the first firefighters arrived at the Underground station to see passengers with bloodied faces and covered in soot coming up from the tunnel.
Mr Shaw said he felt the "urge" to head straight to the stricken carriage but was stopped by his senior officer, Aaron Roche.
Despite knowing that a "distressed" member of British Transport Police had already been onto the train, Mr Roche still dismissed his repeated pleas to act.
"You kind of feel a bit useless when you are standing around not doing much," he said.
"You want to assist the situation and you want to just continue with the job."
Earlier, the inquests for the 52 victims of the 2005 London terrorist attacks heard how the rescue effort was hampered by confused instructions which meant a team of firefighters was dispatched to Euston Square rather than to King's Cross.
Christopher Coltart, representing seven of the victims' families, said: "In the context of what was happening that morning, that was a disaster, wasn't it, frankly?"
"It was unfortunate, yes," Mr Shaw replied.
The inquest, at London's Royal Courts of Justice, also heard how poor radios meant firefighters had to return to ground level to call for more medical supplies, something they found "deeply unsatisfactory".
Suicide bomber Lindsay, 19, killed himself and 26 others when he detonated his device on a Piccadilly line train between King's Cross and Russell Square stations in London at about 8.50am on July 7, 2005.