Controversial thriller about Luci, a disturbed teenager, seducing adoptive father and mother - Hayden was 15 when she filmed this.
Luci and her youthful lover board a London Transport AEC Routemaster, although it's not definite that the RM seen in the First shot is the one used for the boarding scene or the interiors:
This, however, is LT's RTW43 (KGK543), an all-Leyland PD2/3, which at the time of filming was being used as a driver training bus, hence the L plate:
On a second journey by Routemaster, what appears to be a Commer Avenger/Duple Corinthian passes at speed: