IT IS not often that an elderly couple would make up their son's bed with satin sheets and spread rose petals in readiness for a visit by a sex worker.

But this is no ordinary birthday celebration for Mark, who has cerebral palsy and yearns for an intimate relationship. Mark is confined to a wheelchair and speaks via an electronic communication board but his eyes light up at the prospect of an overnight liaison with Rachel Wotton, a Sydney sex worker of 17 years.

The liberating, unexpectedly romantic encounter features in independent director Catherine Scott's latest documentary Scarlet Road, which is among the films vying for the $10,000 Foxtel Australian Documentary Prize at this year's Sydney Film Festival.

The full program will be announced today by the festival director, Clare Stewart, and will include many Australian premieres, including films fresh from the Cannes film festival, which begins today.