A doctor who survived the 7 July bomb attack at Aldgate has spoken of her frustration over being unable to do more to help the victims.
Gerardine Quaghebeur said she had no first aid supplies and could only offer comfort to the injured.
The coroner hearing the inquests said Dr Quaghebeur underestimated the importance of what she did.
Victim Carrie Taylor's father thanked her for staying with his daughter so she was not alone in her final moments.
Dr Quaghebeur, 50, a consultant neuroradiologist at the John Radcliffe Hospital in Oxford, was travelling to her second job in London in the second carriage of the Circle line train, when Shehzad Tanweer detonated his bomb.
She said she was about to evacuate the train following the explosion when she looked to her right and for the first time saw the dead and dying passengers in her carriage.
One of the injured, professional dancer Crystal Main, looked at her and said, "You can't be leaving us - you're not going to leave us?"
The doctor replied, "No, no, I'll stay", and asked if she could remain.
Miss Taylor, 24, appeared to have spinal and head injuries and Dr Quaghebeur said she cradled her in her arms to comfort her for about an hour.
But she said she did not feel she achieved anything on the stricken train.
"I am a doctor, but really I was no more professional - what can you do in a situation like that?" she asked.
"You can't do anything, you're completely on your own, you have no first aid to give, you have no airway to give.
"You have absolutely nothing to give other than to maybe comfort the people that are alive."
'Courage and humanity'
Miss Taylor's father John asked her why she stayed on the train.
Dr Quaghebeur replied: "It was to comfort her and it was to comfort some of the other people in the carriage and not leave them alone."
Mr Taylor said: "Thank you very much for that."
He also asked her: "It was your opinion that Carrie would not have survived unless she got medical aid immediately?"
She answered: "Nobody would survive an injury like that without aid. I still don't know whether she would have survived if aid had come earlier."
Dr Quaghebeur said the emergency services did not arrive to help for some time, but in the meantime other passengers continued to evacuate.
She said: "They all walked past in a row and nobody came. Well, that's not true. A couple of people came to take pictures, which I got really annoyed about and I got cross. I think a policeman said they would stop [them] doing that."
After she completed her evidence, the coroner, Lady Justice Hallett, told her: "You offered comfort and assistance to some people in dire distress and dire circumstances.
"In my judgment you behaved with great courage, determination and humanity, and there are a number of people who have very great cause to be grateful to you."
Earlier, Mr Taylor questioned one of the last people to see his daughter alive in an emotional exchange at the inquest.
He told survivor Melvin Finn that the young woman he had helped following the bomb was "probably my daughter, Carrie".
Mr Finn told the court that her eyes were closed but she "appeared to be alive".
Asked by Mr Taylor whether his daughter had said anything or murmured, Mr Finn replied: "No, absolutely nothing, nothing at all".
Another survivor of the attacks has described awaking to a scene like a "video nasty" after being knocked out for 30 minutes.
Hilary Collyer told the inquests she asked a fellow passenger what had happened and was told: "I think there's been a bomb, love."
She said she waited about an hour to be taken to hospital after evacuation, despite being classed "priority two".
She said the moment of the explosion was as if someone had "flicked the light switch" and she lost consciousness.
"The way I have described coming to was I felt I had fallen asleep on the sofa and someone had put a video nasty on the telly.
"But I remember coming to with this scene around me just completely disorientated, just wondering what had happened."
The inquest has also heard that police shut down the O2 mobile phone network to the public around Aldgate Tube station after the attacks to prevent overloading.
A senior officer from City of London Police invoked powers to restrict use of the network to members of the emergency services with special handsets.
The inquests into the 52 deaths are expected to take up to five months.