John Mills, 57, husband of Barbara Mills, staggered into his house after leaving a trail of blood along the street.
Inner London Crown Court heard that Mr Mills, a businessman, was walking 40 yards from his car to his home in Albert Street, Regent's Park, London, when he was confronted by six teenagers armed with a knife and a truncheon.
He told the jury that they began punching him. "They looked very aggressive and it did not seem very sensible to get severely beaten up for the value of the contents of my wallet. So I took it out of my pocket and it was snatched from my hand."
The youths fled with the wallet, which contained pounds 100 in cash as well as credit cards and photos of his wife and children.
Peter Clarke, for the prosecution, said: "One of the group barged Mr Mills with his shoulder and Mr Mills fell to the kerb and was hit on the head with a black truncheon. The whole group then closed in."
Mr Mills did not immediately realise he had been stabbed. He said: "I was about to walk back home when a car stopped and the driver asked if I was all right. I said I thought I had been mugged but did not feel too bad. She said `I don't think you are all right. You have got blood all over you'."
He staggered back home to his wife. "There was an enormous amount of blood. I left a trail of it up the street and on the door when I waited for it to be opened. I was just dripping with blood," said Mr Mills.
An ambulance was called and Mr Mills was rushed to hospital. "He had a severed artery at the back of his abdomen and had lost a litre of blood before emergency surgery repaired the artery. The wound could have killed him," said Mr Clarke.
The jury was told that Bernard Enerio, 17, was arrested nearby and found in possession of a butterfly knife that still had Mr Mills's blood on it. He also had the wallet, which was empty of cash.
The Crown accepts he was not the knifeman, but claims he wielded the cosh. Mr Enerio, of no fixed address, denies wounding with intent, robbery, and possessing a truncheon on 30 May this year, but he admits possessing a bladed weapon.
The trial continues.