It's on the DVD set for the "World at War" series as an extra add-in. I found a copy at my local Barnes and Noble.
The series itself is a 24-part documentary narrated by Laurence Olivier that won awards for documentary achievement. It's not cluttered with the revisionism that is so common today. Ambrose looks a lot different in this interview -- he's got shoulder-length hair and one of those big sweaters that the college types wore in those days.
I must have seen the series 50 times on videocasette -- no, I'm not kidding -- and I learn something new every time I see it. There's an hour devoted to the decision to drop the bomb that ranks as among the best documentary features I've ever seen, mainly because it was done when some of the decision makers were still alive to tell first-hand of their processes. Highest recommendation.
It rates up there with 'Victory At Sea'