For most of the two years since the death of Lakhvinder Reel, known as Ricky, his family have had a fraught relationship with the Metropolitan Police, accusing the force of failing to investigate the death properly. But yesterday Ricky's mother, Sukhdev, joined Detective Chief Inspector Sue Hill to relaunch the police inquiry, as an enhanced photo image was released of two men walking in Pratt's Passage alleyway, Kingston upon Thames, at 12.10am on 14 October 1997.
Police believe that only one minute later the pair - both white males aged 18-30 - may have been involved in a racial incident with Ricky, 20, and his Asian friends.
Racial insults, including the words "Oi Paki! Shut up!" were shouted at the Asian group, who were on a night out. As a fracas broke out and punches were thrown, Ricky, a Brunel University student, fled. His body was later discovered one third of a mile away in the River Thames.
Police yesterday also released two further images taken from closed-circuit television cameras minutes after the fracas took place in the Clarence Street precinct. One shows three men in dark clothing, one with an umbrella, and the other pictures a man or woman in a hooded jacket.
Mrs Reel said yesterday that she would not be able to sleep at night until she knew how her son had died.
"All I can see is Ricky running and I feel guilty because I was not there to save him. I feel I have let him down as a mother." She said that 22 months after Ricky's death she often went to Kingston shopping precinct in the early hours of the morning - "when nobody is going to see me" - just to stand and cry.
Deputy Assistant Commissioner John Grieve, head of Scotland Yard's Racial and Violent Crime Task Force, said the mystery was a challenge to the whole of society. "Either we think this is important and we try and do something about this as a society or we might as well give up about all the course of events that Sir William Macpherson has put in train."
Mr Grieve said that the two men involved in the racial incident would certainly have boasted about it to their friends, family or girlfriends. But Det Ch Insp Hill pointed out that "evidentially" she could not link the fracas in the precinct with Ricky's death by drowning in the river.
Police believe the two white males - who are 5ft 10in and 5ft 6in - may have boarded a 281 bus to leave the area. They have conducted extensive interviews with local businesses, taxi drivers and nightclubbers but have few leads to go on. Anyone with information is asked to call 0171 230 4374.