Police have released CCTV images after a passenger was threatened with a knife on a Crystal Palace to Dalston Junction train.

British Transport Police officers want to speak to this man in connection with an assault on a 20-year-old man at midday on August 29.

Police say the victim boarded the train at Crystal Palace and a man, who appeared to be smoking cannabis, approached him.

The passenger asked the man to stop smoking but he became threatening and pressed a knife concealed in his sleeve against the victim’s face.

The man then took some money out of his own pocket, asked the victim to remove his shoes and told him he wanted his laptop and mobile phone.

The victim refused and tried to walk off. The man punched the victim in the face, before getting off the train at Sydenham.

Detective Constable Denis Mahoney said: “Fortunately, the victim did not sustain any serious injuries, but this was a frightening assault which, given that the individual was carrying a knife, is particularly concerning.

“After reviewing CCTV from the train, I am issuing an image of a man who I think has valuable information about the incident.

“Do you recognise him? Please get in contact with BTP.”

Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference SSUB/B4 of 21/10/2014.