He added: "As I got near him I swung at him with everything I had as hard as I could, straight through his head, trying to go for like a knock-out blow."

His blow made the attacker "yelp in pain", but then found himself surrounded and fighting desperately for around 90 seconds.

During the fight, he was stabbed just above his right eye, and suffering severe wounds to his head, left leg and left hand.

The officer, who has worked with BTP for just under two years and was a PCSO with the Met for around six years beforehand, said a blow to his head plunged him into "instant darkness".