It was lovely to see the old news footage of Unity and her parents, Lord and Lady Redesdale, returning to the UK in 1939 after Unity's failed suicide attempt. The highlight for me was the interview with Diana Mosely filmed in 1999. Diana, like her younger sister Unity, was a friend and supporter of Hitler before and during the second world war. Diana died in 2003 and was 89 at the time of the interview. The main premise of the documentary, outlined by the presented Martin Bright in his New Statesman Blog, was that Unity was pregnant with Hitler's baby when she returned to the UK. Unfortunately for the documentary makers the only eye witness who consented to be interviewed said that Unity didn't have a baby.
You can view the complete documentary on 4 on Demand. It is free for 30 days after transmission but may well continue to be available for free after that. I have a copy on my Sky+.