A woman held the victim of an assault down during a “violent and sustained” attack on a train.
Now British Transport Police are calling on the public to identify these two people pictured in CCTV footage.
The attack took place on the 2.04pm train from Theobolds Grove to Liverpool Street on Tuesday May 20.
A man and a woman with a Staffordshire bull terrier boarded the train at White Hart Lane station.
A few minutes later, the man attacked another passenger who was already sitting on the train.
Detective Constable Gemma Jones, who is leading the investigation, said: “The attack, which appeared unprovoked, was violent and sustained. When the victim tried to defend himself the woman began holding him down to enable the man to continue his assault.”
The victim, who is believed to have boarded at either Theobalds Grove or Turkey Street stations, left the train at Bruce Grove to get away.
Both suspects got off the train at Seven Sisters station.
Police say they have been viewing CCTV footage and interviewing witnesses in the time since the attack.
DC Jones added: “We believe the man and woman pictured in these stills will have information which can assist our investigation so it is vitally important that we speak to them. If you can tell us who they are, we want to hear from you.”
Anyone with information should call British Transport Police on 0800 40 50 40, text them on 61016 quoting ESUB/B6 of 08/08/2014, or call independent charity Crimestoppers anonymously on 0800 555 111.