Metropolitan Police detectives said two males targeted the youngster on the evening of Tuesday 11 July on Hampstead Road in Camden, not far from Regent's Park, as she was walking home at around 8.30pm.

One of them threatened her with a knife and told her to hand over her phone and give him the password.

Once she had provided the password, the suspects let her go and she ran away.

A 16-year-old boy has been arrested on suspicion of robbery and bailed pending further enquiries, while a CCTV image of the second suspect has been released.

Sergeant Max Pennington, from the local policing team in Camden, said: "We have made good progress with our investigation, however we are still keen to identify the other person involved.

"This was a terrifying robbery which took place in broad daylight and we think there will be people who witnessed the incident or recognise the man pictured who can help us to find him and we would urge them to get in touch."