9/11: The 73 minutes that changed my life

Getting down on his knees, Van Why saw that the man had a serious head injury. He appeared to have been hit by a putty knife that had fallen from one of the buildings and was lying nearby stained with blood.

"Another man stopped and gave me a denim jacket which we put over the open wound and then I remember seeing his watch on the street beside him and I put it in his pants [trouser] pocket. We turned him over and he had a work tag with a name."

With tears falling and his voice cracking, Van Why goes on: "My biggest regret is that I didn't look to his tag to see what the name was. I could have found his family and told them that there were people with him."

An ambulance arrived and it required several people to lift the man on to the stretcher. Van Why stroked his arm and told him he would be fine.

Realising he had left his mobile phone in the office, he began asking strangers if he could borrow one to get the message through to his parents that he was OK. But none of the phones were working, so he went into a cafe and used a telephone there.

When he emerged, he heard a deafening sound. He looked to his left and saw a wall of grey smoke coming towards him. The South Tower was collapsing.

For the second time that morning, he started running. The time was 09:59, 73 minutes after the first plane flew into the North Tower.

By the time he got to his apartment on 43rd Street, after deliberately avoiding the area around the Empire State Building, it was approaching noon. The North Tower had also collapsed, but Van Why had been far enough away to not hear it.