On a damp Friday morning in downtown Los Angeles I find myself standing in a chilly, rather shabby warehouse watching a group of bearded, tattooed technicians haul cameras and lighting equipment up a flight of stairs. Feeling sheepish that I am standing idle while they huff and puff, I offer to lend a hand and am soon enlisted fetching plastic bags full of cables from a Jeep parked outside.

To get up the stairs with my bags, I have to walk past several other camera crews getting ready to film. One group is here to shoot an episode of Top Chef, the culinary reality show presented by Padma Lakshmi (better known in Britain as Salman Rushdie's ex), another crew is from the E! entertainment channel, here to film an episode of Chelsea Lately, a late-night comedy chat show. The people I am here to meet occupy a more notorious corner of the media industry. They are among the thousands of pornographic actors and film-makers living and working in the Los Angeles area: the sex professionals who turn private passions into everyday paid employment.