Henderson played Ursula Blake in the 2006 Doctor Who episode Love and Monsters who was a member of L.I.N.D.A, a secret organisation created by humans on planet earth to track down the Doctor. Harry Potter fans first met Henderson in Harry Potter and the Chamber of Secrets as Moaning Myrtle, a teenage ghost who haunts the girls' toilets. Both of these characters met a somewhat sticky end. Myrtle was petrified to death by the Basilisk while Ursula was a victim of the Abzorbaloff but was later restored as a slab of pavement. You couldn't make it up.