The show was based on the popular books and blog by the pseudonymous "Belle de Jour" and followed the life of Hannah, also known as Belle (Billie Piper), a high class call girl. This episode, which was the seventh of the fourth season, was the penultimate episode of the full series run.
So, we have a call girl… but a vampire…
|Billie Piper as Belle|
|black and white moment|
A fleeting visitation of someone pretending to be a vampire for role play purposes. The episode's imdb page is here.