Victims of slavery can be British - the story of one such woman is told in the memoir Secret Slave. Under the pseudonym Anna Ruston, she writes about meeting a taxi driver she calls Malik when she was 15.

He was kind to her but when she went to his house expecting to meet his family, she was held captive and subjected to sadistic sexual and psychological abuse for the next 13 years. Eventually she managed to escape.

She says the police later asked her to give a statement, but she refused because she feared for her life.

She speaks to our reporter Samantha Haque - her words revoiced to protect her identity.