This is the face of a drug-fuelled teenager who robbed two 13-year-old boys at knifepoint in an Oxford underpass.

The youth approached the two teenage boys beneath Ferry Marston Road, near The Cherwell School, at around 5.30pm on Monday.

He threatened them with a penknife and forced them to hand over their mobile phones.

Police have described the robber as white, around 5ft 11ins tall, of muscular or fat build and aged between 17 and 18.

He had a small scar above his right eyebrow and was wearing a hooded top with gold patterns on it and black Adidas tracksuit bottoms.

Det Con Claire Routledge, of Oxford robbery team, said: "The offender was riding a black mountain bike and the victims believe he may have been on drugs as his pupils were dilated and he was struggling with his words."

Anyone with information is urged to contact police on 08458 505505 or Crimestoppers on 0800 555 111.