A father is believed to have been brutally stabbed to death in a case of mistaken identity outside a pub.
Christopher Foster, 34, was attacked while having a cigarette with a male friend in an alleyway outside St Christopher's Inn in Borough High Street, Southwark, near London Bridge station.
Officers were called to the scene at about 11.45pm on Friday night and Mr Foster, from Walworth, south east London, was taken to the Royal London Hospital in Whitechapel, east London, where he died at 1.05am on Saturday morning.
Witnesses said they saw seven suspects wearing hooded clothing carrying baseball bats and at least one knife.
Mr Foster, who worked in administration for a firm of lawyers, was not married and was a father of a four-year-old girl. No more details of his personal circumstances were available.
An incident room has opened at Barking under Detective Chief Inspector John Sandlin, who said: "At this stage of our investigation, this appears to be a case of mistaken identity.
"I am keen to identify a group of males who were seen running from St Christopher's Inn along Borough High Street towards Elephant and Castle immediately after the stabbing."
A 32-year-old woman was arrested today on suspicion of assisting an offender. She was taken to an east London police station where she remains in custody.
Anyone with information that might assist the investigation was asked to call the incident room on 020 8345 3865 or to remain anonymous they can call Crimestoppers on 0800 555 111.
Mr Sandlin said later that it was thought it was a case of mistaken identity because the group had gone on to have an altercation nearby with another man, who managed to run away from them.
"I think they were looking for someone," he said. "Chris was an innocent man. There was no reason for him to have been attacked. He was a working guy out with his mates having a beer.
"I need to find some witnesses who have seen this group in Borough High Street or the alleyways that run off it, before the incident, or afterwards, when five of them ran off down Mermaid Court."