The man, who was in his twenties, was carrying a bible when he scaled the 20ft overhanging chain-metal fence surrounding the Asiatic lion enclosure in Regent's Park at about 11.15am.
He was attacked by three male lions - a five-year-old and two one-year-old cubs. Simon Tonge, the senior curator, said: 'One had him by the neck and the two younger ones were biting his legs.'
The adult lion, Arfur, was responsible for a similar attack on a schizophrenic who climbed into the lions' enclosure last New Year's Eve. Ben Silcock suffered chest and stomach injuries.
Yesterday's attack was said to be less severe. The shouts of visitors and the screams of the victim alerted a keeper. About 30 members of staff were involved in the rescue.
The man was taken to the Royal London Hospital, Whitechapel, by air ambulance. Last night his condition was said to be serious but stable. The man was not under the care of a a scheme for the mentally ill.
The zoo pledged to review safety in the light of yesterday's incident but the lions would not be killed, Mr Tonge said. They had behaved in a completely natural way by attacking a stranger.Reuse content