My Architect

Each of these extras is excellent, enhanced by Nathaniel Kahn's charm and intelligence. As the writer/director/creator of this highly personal documentary, he is not afraid to talk of emotions, fears, doubts and any other aspect of his life.

The Director's Q & A has him sitting on a stool in a small movie theatre, answering questions from a receptive, well-mannered audience. He's talking about the film that took him five years to make, the search for his father, an emotive subject and one that has no template.

"Finding the structure of a film is not unlike finding the structure of a building," he says.

This feauturette gives him an opportunity to show some of the deleted scenes, all of which, without exception, are worth watching. Because he decided to treat the film as a journey, rather than a structured cinematic biography, after introducing someone and talking to them, he never goes back, which means there is a stack of good stuff on the hypothetical cutting room floor, which is given the benefit of a DVD airing right here.

He uses the Q & A as an appendix to the main film. As well as answering questions from the stalls, he inserts the best that has been left out, including the buildings that couldn't be shown and architects of every nationality, discussing Louis Kahn's extraordinary life. He includes a telling moment at a college lecture when his father, in response to a student's question, remarks, "I can truly say I have accomplished nothing."

The UK Exclusive Director Interview is a straight-to-camera talking head. The interviewer, Tom Dawson, is heard but not seen.

Again, what makes this riveting to watch, or rather listen to, is Nathaniel Kahn's personality. His eloquence never appears forced, nor patronising, and you feel that he speaks from the heart.

During this "search to find my father," he had to enter many closed rooms. "You don't know where you are going at the start." Nothing was predictable, nothing scripted. He shot the film chronologically, so that the journey was a revelation, even to him. "I started in one place and ended in another. That's not concocted."

He doesn't like doing pre-interviews, because when you go back with a camera, it feels unspontaneous and repetitive.

"Filming architecture is very difficult. It can be so dead. It took a long time to make these buildings emotional. I tried to find ways of bringing them to life."

He ended up with 20 hours of footage, after five years. "The reason it took so long was we kept running out of money. To do this kind of thing, you have to quit your job. I did."

As well as the emotion involved in such a personal venture, he had no idea how it would map out, or whether he would have a film at the end.

"If it's not a risk, if you're not on the high wire, what's the point?"

By being brave and opening those closed doors, he reaped untold rewards. When he was growing up with his mother, he thought of his father as a heroic figure, hardly real.

"In making the film, he became a man."