The photograph albums and talking about memories of their mother in a deep-felt loving way was real and touching.
It did made me feel sad and a little cranky about their father, Prince Charles, who was carefully never mentioned unless of course it was utterly necessary.
For example in the solemn file behind in the funeral cortege, a shot of him pale and thin-lipped climbing from a plane after a tour of Korea where Diana looked so miserable and downcast you felt the urge to give her shoulder a wee squeeze. It was so obviously the end of their marriage, and, of course, a fast snippet from their wedding day.
The brothers said they wished they had spoken more about their mother earlier and they even talked about how terrible it was they had not been able to help or protect her when she was alive.
I found it difficult seeing again the way Diana was hounded by the paparazzi, so cruel, vicious and unrelenting.
And now years after her death how all royal talk of her has become minimal and very measured. It was pretty obvious it was about Charles wanting to move on with his life and Camilla.
The brothers laughed when they talked about Diana as a granny and how she would have encouraged her grandchildren to be naughty and fun. Nothing was mentioned about other granny Camilla.
They were both sad the phone call from her hours before she was died was really just another call where they couldn't wait to head off outside and get on with their games. Although William said he remembered the call well he said he would never speak about it.
Twenty years on it still feels like a tragedy where the world lost a beautiful, albeit flighty princess.
Despite what naysayers still grizzle about it was clear that Diana was a fine mum with a love in abundance. Her sons' memories, though softened by time, were deep and still a bit guarded.
This documentary was family grief portrayed with a soft focus and a much remembered love.
