The Metropolitan Police said the victims, aged 34, 39, 42 and 52, were all found at the scene with stab wounds. A 47-year-old woman has been arrested on suspicion of possession of an offensive weapon and assault. A London Ambulance Service spokesperson said: "We sent an ambulance crew, a paramedic in a fast response car and an incident response officer. "We treated four patients at the scene and took them all to a major trauma centre as a priority by road." No further update has been given on the extent of their injuries.