Cycling along a street in the east of Amsterdam five years ago on Monday, Theo van Gogh, the outspoken Dutch film-maker, was shot and, as he slumped on the ground, his murderer slit his throat and pinned a letter to his dead body.

The killing of Van Gogh, targeted by a second-generation Dutch Moroccan because of a film critical of Islam and notorious anti-Muslim remarks, shocked the nation and intensified an already heated debate about the "Dutchness" of the country's 1m Muslims.