Avril Lavigne and ex-husband Deryck Whibley photographed leaving a party in London together just four months after she filed for divorce.

Avril and the Sum 41 rocker called it quits late last year after three years of marriage, citing "irreconcilable differences." She has since been linked to The Hills hunk Brody Jenner and actor Wilmer Valderrama.

BUT... Avril and Deryck were sharing a car together after the "Alice in Wonderland" premiere in London on Thursday night.
TMZ HAS PIC