She's bad Buffy, if you will, and for whatever reasons - that I care not to explore - I have an empathy with Faith. We were once interviewed by an American magazine and they said “What character do you relate to the most?” I immediately said, "Faith" and everyone in the room took a healthy step back away from me! She is psychotic, but it is a confluence of things with Faith.

You can't underestimate Eliza Dushku’s performances and Michael Gershwin did an amazing job of directing that episode. Ray Stellar was the cinematographer on that episode and he really went to town. Then you've got Sarah of course, who introduced this… I think this is when we actually said the Patty Duke metaphor. You've got the bad cousin, basically: Patty Duke with the identical cousin.

Throwing Eliza into the mix makes Sarah respond in a certain way and Sarah is an extraordinary actress. I think that this two-parter gave her an opportunity to do some stuff that she'd been itching to do for a while. It 's very much a team effort and I'm always delighted to have a crack at Faith because I love writing her dialogue and I just love writing her take on her place in this world.

BBC : Did you have any influence on the development of the subsequent Angel episodes? Did the writers seek your opinion about how to treat her in those episodes?

Doug Petrie: No, having thoroughly blown my own horn and saying, "This is my character": baloney! I had nothing to do with it! I thought those Angel episodes were excellent and outshone, in many ways, anything I've done with the character. It's just more proof at the Buffy universe belongs to all of us.

I thought that those episodes were the great Russian novel and Faith's quest for redemption is an endlessly interesting thing to me. Hats off to the Angel writers for putting those episodes together, but no - with humility - I must say I had nothing to do with them.