Police have issued CCTV after a man was left with serious injuries following an assault in central London.Officers were called at around 00:40 on Saturday, June 3, to reports that a man had collapsed after being assaulted in Trafalgar Square. The 50-year-old is in hospital in a critical but stable condition. The victim was assaulted in the area outside the National Gallery - no weapons were involved.Two male suspects are believed to be involved and the Metropolitan Police are appealing for information.