Bruce Forsyth talks about being the first subject of Who Do You Think You Are? (BBC1, Monday, July 19) and discovering his darkest family secrets…

You appear very moved at the end of the programme when you go into the story of your great grandfather, Joseph Forsyth Johnson, a famous landscape gardener who died almost penniless…
“I was a bit choked in the final scenes. Before then I didn’t have a high opinion of him, but when it came to the end, he was pretty ill and it was rather sad.”

How did it all start?
“I received a letter from a lady in Georgia, America, suggesting that she was related, and that their great grandfather was a bigamist. I was surprised! That letter started the whole thing off and then we went on a kind of safari trying to find out all about him.”

Did you find any parallels with your own life?
“There’s definitely a similarity between us. Like him I have six children – three daughters from my first marriage, two from my second marriage and my son, who my darling Winnie [Bruce’s third wife, Wilnelia Merced] gave me. The only thing is that we haven’t got evidence that he looked after them as much as he should have done – my family is so together.”

So he was a real black sheep?
“I’m the black sheep of the family, not him, let’s get that straight. I’ve always been the black sheep, I’ve always been proud of it and that’s what I’m going to be for the rest of my life.”

Was it good meeting the American side of your family?
“Yes. I’m planning to stay in touch with them. There was one old lady who was absolutely marvelous. She was 92 and there was such a resemblance with Joseph.”

How have your own children reacted to the show?
“They have not seen it. I’ve decided they’re all coming to the house and we’re going to put the DVD on and show them altogether. It’s because I can’t go through it again and again. See, I’m going to start crying now!”

Did you find out all you wanted about him?
“No. There are so many other things I would have loved to have found out. I wish we could have got him there somehow, even in spirit. I think we should have had a seance and got him to come back and found out the things we were still dying to know!”

What especially would you have liked to find out?
“I would have loved to have known where all his money went. In the Edwardian times the creme de la creme of London did a lot of betting, so I wonder whether he got into that crowd. That would have been very sad because I’ve always been a non-gambler. When I was very young, growing up in the business, I saw people lose all their money, so I’ve always taken care of mine.”

What’s next for you?
“I’m going to have a rest because this has taken more time than I thought. I hardly saw any Wimbledon this year and I love Wimbledon!”

What about doing Strictly again this year?
“I only ever sign for the series during the summer and the summer’s only just begun, but things are looking good. It seems I’ve been leaving the show ever since it started. Every year they trot out all the people that are going to take my place, but nobody’s tried to murder me and get the job yet, so I think it’s still open!”