Two firefighters died in a burning building because of communication problems and an inadequate water supply, an inquest jury has ruled.
The two firemen were the fourth team sent into the basement
Billy Faust and Adam Meere died fighting an intense fire in Bethnal Green, east London, in July 2004.
The inquest heard a hose reel was burnt through and more powerful water jets were not used because officers did not realise the strength of the flames.
The fire brigade said lessons had been learned and changes made.
Mr Meere, 27, had been a fully qualified firefighter for two months when he and Mr Faust, 36, entered the basement of the three-storey building - where the fire is thought to have been caused by a cigarette.
They were among 50 firefighters called to the scene and two people were rescued from the roof.
The inquest heard, however, firemen had not realised how intense the fire was.
As a result, powerful water jets were not used to tackle the flames. The inquest heard 30 minutes passed between the order being given to use a fire hydrant, and the water being used.
It was also claimed that the two men were still in the basement when colleagues opened doors and windows to ventilate the building - said to have been followed by a crack and "vroom" sound.
About 50 firefighters were called to the blaze
It was claimed the flash-over - the moment when all flammable material ignites simultaneously because of the intense heat - may have killed the men.
The jury found there had been a failure to recognise that ventilating the building might have caused an escalation in the fire.
Coroner Andrew Reid paid tribute to the bravery of firefighters who risked everything to save their colleagues by going back into the building.
"Sadly those efforts were in vain," he said.
Mr Meere, from Westcliff-on-Sea, Essex, and father-of-three Mr Faust, from Banstead, Surrey, died later in hospital - the first firefighters to die on duty in London for more than 10 years.
Dr Reid said he would be writing to the relevant authorities urging that the accident investigators' recommendations were followed up, to prevent more deaths.
He added that the firefighters on the day had never seen the "forthcoming catastrophic tragedy evolving".
The Fire Brigades Union welcomed the verdict.
Regional chairman Gordon Fielden said the operational readiness of London Fire Brigade was "at the poorest standard it's been for over 30 years."
He also called for an inquiry into the way the first accident report was compiled.
Mr Faust's widow Michelle, 38, said: "I feel pleased that justice has been done despite all their efforts to try and cloud it.
"I hope that this will stop anyone else going through what we have gone through."
London Fire Commissioner Sir Ken Knight said the fire was "one of the most difficult and complex" they had ever considered.
He said:¿ In any tragedy such as this there are lessons to be learned.
"The recommendations made by the accident investigators were considered in detail at any early stage and many of them have already been implemented."
But Mr Meere's father Pat, who had been a fireman himself, said after the verdict: "I came here two weeks ago with my pride intact.
"Now I despise the fire brigade for what went on and just want them to say mistakes were made and they will put them right on the strength of what went on."