Tori Allen-Martin

For the past 3,723 days, Marnie has been experiencing an incessant barrage of graphic x-rated thoughts. Unbeknown to Marnie, she's caught in the grip of a remarkable form of obsessive compulsive disorder - nicknamed 'Pure O'. Moving to London, Marnie is desperate to find out what's wrong with her.

Nothing ever goes to plan for the Jessops – and son Sam has caught it all on his camera.