Police are searching for two heroes who used a skateboard to restrain a suspect after a man was stabbed to death in Oxford Street.
The Met have issued a picture of the duo, who rushed to help the victim following the attack on Thursday.
In a statement detectives said one of the men used his skateboard to “subdue” 25-year-old Tedi Fanta Hagos, who has been charged with murdering victim Stephen Dempsey.
Detectives say the men led efforts to stop the suspect, but did not stay at the scene to speak to police.
They have been praised for showing “great courage” and police say their actions “potentially prevented others from being attacked”.
The force they used was “entirely reasonable” and is “not in question”, investigators said.
Hagos did not sustain any lasting injuries.
Police said in a statement: “Their key role has only come to light following a review of CCTV and other video footage of the incident and its aftermath.”
The attack happened at around 8pm on Thursday on the famous central London street.
Tragically the victim, who was 60, died the same day.
Detective Chief Inspector Vicky Tunstall, who is leading the investigation, said: “In addition to being immensely brave, we believe these two individuals may also be key witnesses.
“In stepping forward as they did to apprehend a violent individual, they showed great courage and potentially prevented others from being attacked.
“I want to be clear that while they used force to subdue the attacker, those actions were entirely reasonable and are not in question.
“They can be assured that we wish to speak to them solely as witnesses.”
The pair are urged to call the incident room on 0208 785 8099. They can also get in touch with detectives online using this form.
Fanta, who has a previous address in Swansea, appeared at Westminster Magistrates’ Court on Saturday.
He was remanded in custody to appear at the Old Bailey on Tuesday.
Police on Friday described it as a “random, unprovoked” attack and a murder investigation was launched.
Speaking on Friday, DCI Tunstall said: “This is being treated as a random and unprovoked assault and we are not actively looking for anybody else in connection with the incident.
“I would like to reassure the public that his is not believed to be linked to terrorism.
“It is clear that this area of Oxford Circus was very busy at the time of the attack.
“Members of the public intervened to detain the suspect and I hope to trace and speak to them, to secure their accounts and offer support. In particular, I would like to trace two young males with skateboards who led this intervention.
“I am appealing to any person who witnessed the assault, or who has mobile phone footage, to contact us. I am also appealing to the owners of any passing cars with dashcams to check whether they have recorded the incident.”