Richard Osman has discovered that his four-times great-grandfather formed an amateur detective gang to try and solve murders.
The Pointless host - author of bestselling crime novel The Thursday Murder Club, about a group of friends in a retirement village who investigate crimes - learned on BBC show Who Do You Think You Are? that his book mirrors the real life of his ancestor Gabriel Gilliam.
Gillam, a fisherman born in Brighton in 1789, discovered a dead body and became involved in one of the biggest murder trials of the 1800s.
Read more: Why is Richard Osman leaving 'Pointless'?
Osman told the Radio Times: "Given the books I write, you just couldn’t make it up
"It was extraordinary to discover that Gabriel Gillam formed an amateur gang of detectives.
"It felt like it would make a good Sunday night TV drama. There are a million stories about the British upper class, from Downton to Bridgerton, but very few about poor communities."
He added on Twitter: "This was genuinely true. A remarkable coincidence."
The Thursday Murder Club - about a group of elderly amateur sleuths living in Kent - was published in September 2020 and quickly topped the Sunday Times bestseller list.
The global film rights were bought by Steven Spielberg’s production company Amblin Entertainment and the story is currently being adapted for the big screen.
Gillam was also revealed to have been charged and fined for smuggling food and tobacco.
Osman was delighted, exclaiming: "I said right at the beginning, I'd love to find a pirate and a smuggler will do me."
In his episode of the BBC show, which investigates the family tree of participating celebrities, Osman chose only to learn about the heritage of his mother's side of the family.
That is because, as he has spoken publicly about before, his father walked out on the family when he was nine-years-old.
Osman, 51, grew up in Haywards Heath, West Sussex with his mother Brenda Wright and older brother Mat Osman, of the Britpop band Suede.
Osman said: "My dad's side of the family wasn't something I was interested in because that's not the family I grew up in. It would, in a funny way, be like learning about strangers."
Watch: Richard Osman doesn't think Alexander Armstrong will leave Pointless