Extracted from Harry Potter Film Wizardry.
As we learn in the third book and film, witches and wizards stranded in the London area have their own designated Knight Bus.
The bus featured in the film was specially built using components from a genuine London Transport Routemaster bus – a red double-decker model first introduced in 1956 that remained in service for almost fifty years.
As the Knight Bus is a triple-decker, John Richardson’s special effects department cut the top off the Routemaster, added an additional level, put the top deck back on, and had it repainted purple. A second Knight Bus was constructed for stunt work using another rebuilt Routemaster.
This double was fitted onto the chassis of a commercial coach that had an engine powerful enough to pull two tons of added lead weight – necessary to counterbalance the extra height so that it didn’t tip over when going around corners.
One of the logistical problems encountered when filming with the Knight Bus was getting it to and from the various locations in London.
‘We had a team with a crane permanently on call,’ John explains. ‘We’d have to take the top off, transport the bus, the top, and the crane, and then put it all back together again before we could start filming!’
A studio set for the interior of the bus was built on a moving gimbal so that it could be rotated and tilted to mimic the Knight Bus’s erratic movement. The interior was fitted with sliding bedsteads, a swinging chandelier, and the now-iconic talking shrunken head – an addition to the films that J.K. Rowling approved of heartily, saying: ‘I wish I’d thought of that.’