A design and technology teacher who survived the 77 bombings will testify at the inquest into the deaths of the 52 people killed in the London attacks.
John McDonald will appear before the Royal Courts of Justice on Tuesday and tell the coroner, Lady Justice Hallett, what he witnessed when a bomb went off in his Circle Line Tube carriage.
Mr McDonald was on the way to his Westminster secondary school when he boarded the same carriage as bomber Mohammad Sidique Khan.
"One minute you are sitting on the train, reading your paper, and the next minute a bomb goes off and all hell breaks loose," he told The TES.
"You're blown into the air, and then a pressure wave pushes you back into the chair. The roof was ripped off the train, and two massive craters were blown in the floor. I was covered in broken glass; one passenger took a lump of metal out of my head. But I knew that, further down the carriage, people would be worse off."
The day before the 2005 attacks, Mr McDonald had delivered a Year 10 lesson in governance and social responsibility. So he felt duty-bound to abide by the instructions he had given his pupils.
"I had to decide: do I walk away from the injured or dying, or do I come to their aid?" he said. "As a teacher, I have a set of values that I try to instil in pupils, and my values were being put to the test."
He repeatedly drew on his teaching experience to enable him to deal with the situation. "Being a teacher, I can stay calm in extreme situations," he said. "In the school workshop, I have lots of machinery going at the same time. You have to have your eye on five things at once. I certainly put that skill to use that morning."
And when two women began to panic, Mr McDonald delivered a classroom "praise burger", softening his instructions with empathy.
"I said I understood that their feet had been injured, but the man I was working with had just had his leg blown off, so would they mind being quiet, please," he said. "I understood their pain, but other people were in a worse situation. After that, they were happy to co-operate."
Following the attacks, Mr McDonald suffered acute post-traumatic stress disorder. He still regrets that his GCSE pupils were deprived of a specialist teacher while he recovered.
"Their education suffered, and it was nothing to do with them," he said.
The day my life changed, Magazine, page 7.