TV Times talks to gardening presenter Monty Don as he uncovers his roots – and finds feuds, philanthropy and some missing marmalade millions…

Why did you decide to do Who Do You Think You Are?
“It has become rather like Desert Island Discs. It is one of those things that you are flattered to be asked to do.”

Were you surprised at what you found?
“I was. I have been brought up to feel like I have a really comprehensive knowledge of my family history. My mother was almost obsessed by it. There were books, stories and portraits everywhere, and we literally had the family tree on the wall. But I didn’t know as much as I thought. What I found out through making the programme is that it was just one stick of the family tree – it made me realise that all history is filtered, and sometimes it is heavily edited.”

Did you cry?
“No. My agent said to me: ‘You’ve got to cry, you know?’ I know the most dramatic episodes tend to have a process of great self-revelation, where people discover things about their pasts that explains their present. But I was dubious about whether that would be the case for me, and to be honest, it wasn’t. It wasn’t an emotional experience at all. Modern media and to a certain extent modern life tends to demand an emotional response, but it is possible to be fascinated or deeply interested by something -and that was more my experience. And I think it was richer for it.”

What about the story of the missing marmalade millions?
“It is a great picture of Victorian commercial life, which was completely unregulated, and a bit like the Wild West. One brother was a thug and the other, my great grandfather, was a manager and although they couldn’t stand each other, they needed each other. They built up this great commercial empire that was even bigger than Cadbury or Rowntree and were enormously wealthy, but the two brothers fought terribly. My great grandfather went to Guernsey and then London because he couldn’t bear to be in the same country as his brother! I didn’½t know about the rift and I certainly didn’t know the extent of the wealth because none of it filtered down to me.

“Actually, what doesn’t appear in the film is that a lot of the money was finally spent on the purchase and restoration of tens of thousand acres of land at Avebury in Wiltshire, which was then donated to the National Trust. So it’s a very honourable place for the money to end up.”

The other key theme of your journey is the heartbreaking tale involving your great, great grandfather, Reverend Charles Hodge, and his nine children being abandoned by their mother. What was it like to uncover this?
“We have never heard about this branch of the family, but it turns out that not only was a painting of Charles Hodge hanging on the wall of the house I was brought up in, but it is also hanging on the wall of the house I live in now. I have seen him every day of my life without ever knowing who he was.”

Are you glad you did the show?
“Yes. I love the way the stories unravel. Going through letters, putting the pieces of the jigsaw together until a picture emerges. It was fascinating. Never at any stage did I know anything about what was going to happen next. I’ve been in television for 20 years and know how things can be contrived, but this programme is admirable for its rigour and scrupulousness.”

Were there any other stories which are not in the final show?
“Yes. One of my forebears was the guardian of James VI who was also James I of Scotland. It is a big story to leave out of the programme, involving Stirling Castle, fighting and bloodshed and the BBC were very apologetic. It also showed that I am much more Scottish than I had thought. And another really interesting thing that doesn’t get shown on telly is that it turns out I am directly related to my wife’s first husband. I didn’t discover that until I made the programme, So that is quite extraordinary. How did I feel about it? It was just funny, it made me laugh, and was a huge surprise to Sarah and I!”

*Monty Don’s Who Do You Think You Are? screens on BBC1 on Tuesday, August 10