OCD brought Thornton and Zevon together

Eccentric actor Billy Bob Thornton became besotted with late rocker Warren Zevon after discovering they both suffered from obsessive compulsive disorder.

The Monster’s Ball star - ex-husband of actress Angelina Jolie - was caught manically inserting and removing his post from the letterbox by Zevon, who recognised the affliction and struck up a profound friendship which lasted until Zevon's death last year from lung cancer.