Officers investigating a sexual assault on-board a Northern line train at Balham have released a CCTV image of their main suspect.

The female victim was assaulted just after 6am on the 3^rd of August as the tube travelled between Elephant and Castle and Balham.

The male suspect also pulled drugs from his pocket and offered them to the victim before telling her he had a knife.

As the train arrived at Balham station, both the victim and the man disembarked the train separately.