A potential witness has contacted police investigating the murder of a teenage model in south London.
Model Sally Anne Bowman was on her way home from a night out
The man went to the aid of a woman who was battered and robbed less than 500m away from where Sally Anne Bowman was stabbed to death in Croydon.
Police said the man, in his early 20s, helped the woman and apparently ran after the robber, who is thought to be the man who then murdered Miss Bowman.
Miss Bowman was killed about an hour after the attack on 25 September.
A police spokesman said the man had contacted police on Monday night and he would be questioned by detectives.
Detective Chief Inspector Stuart Cundy, who is heading the investigation into Miss Bowman's murder, had said: "It is possible that he may have valuable information which could assist with my inquiry."
Knife in waistband
He went to help the woman after she was hit over the head by a robber carrying a metal object and, possibly, a knife in his waistband.
After leaving the woman in Sanderstead Road he is thought to have run after the attacker towards Purley Road shortly after 0300 BST.
Within two hours, 18-year-old Miss Bowman was sexually assaulted and stabbed to death near her home in Blenheim Crescent.
Forensic scientists have linked the murder to a sex attack in nearby Purley in 2001.
Detectives trying to fill in the four-year gap, say the murderer may have been in prison or abroad, but that there may have been other attacks that went unreported.
Miss Bowman's possessions, a white handbag, mobile phone, cardigan and purse are still missing - as is the murder weapon, thought to be a 12cm to 14cm knife.
Her attacker is thought to be white, in his 20s or 30s, between 5ft 9in and 6ft and of medium build with short brown hair.