Anorexia is now the most serious mental illness in the UK, and affects one in 250 women at some point in their lives.

While many make a full recovery, some never do. To find out what life is like inside institutions set up to treat it, Louis Theroux checks in to two of London’s biggest centres for adult eating disorders, St Anne’s Hospital and Vincent Square Clinic.

Louis’s compassion and his tactic of asking probing questions but not passing judgment once again gets him a lot further than many an interviewer with a more obvious agenda.

He gets answers, in other words, some thought-provoking, some sad, some shocking.