A woman, who intervened in a fight on a train, is being urged to come forward by police investigating the death of aspiring rapper Warsame Warsame.

Mr Warsame, 24, died on Monday, March 4, two days after being found unconscious aboard the 1.16pm London Waterloo to Chessington service as it travelled between Wimbledon and Raynes Park stations.

Earlier that day, on the 12.42pm Hampton Court to Waterloo service, Mr Warsame had been involved in an altercation with another passenger as the train travelled to Wimbledon from Raynes Park.

Following Mr Warsame's death, British Transport Police (BTP) launched an investigation into whether he died as a result of injuries from the attack or from an existing medical condition which required regular dialysis.

Now the BTP have issued CCTV footage showing a woman they believe could have information about the alleged assault.

Detective Superintendent Gary Richardson, senior investigating officer, said: “After an altercation broke out between Warsame and another man, a woman on the train stepped in to challenge the man and immediately informed a member of staff.

"From viewing CCTV, we know she boarded the train at Surbiton station and left at Wimbledon.

“I must stress that this woman is innocent and she is not wanted in connection with this assault.

"She was on the train at the time and helped alert staff, who later informed police, and we simply want to find out what, if anything, she might know about Warsame’s death.

“Our thoughts remain very much with Warsame’s family at this acutely difficult and sad time for them, and we will do all we can to try and answer the many questions they have about the circumstances leading to his death.

“We’re continuing to appeal for anyone with information to come forward. Do you know the woman? Are you the woman pictured? If so, we’d like to hear from you.”

Anyone with information is asked to contact British Transport Police on 0800 405040, quoting B5/LSA of 04/12/12.

Alternatively contact the independent charity Crimestoppers, anonymously, on 0800 555 111.

* A 24-year-old man from Wallington, Surrey, was arrested on March 16 on suspicion of GBH. He was bailed to appear in court on April 22.