Comedian and actor Greg Davies adored his dad. “I am so my father’s son,” he says at the start of his episode of Who Do You Think You Are? “He is to this day – obviously, I’m biased – the funniest person I’ve ever met.”

Despite this, Greg’s “embarrassed” about how little he knows about his late father’s Welsh ancestry, something he now wants to correct. There’s also the small matter of his dad’s hints about a “Davies secret”.

At his mother’s house in Shropshire, Greg sees a copy of the birth certificate for his grandmother, Edith. No father is listed. Greg realises that his great grandmother, Elizabeth Thomas, had two illegitimate children before she was married, “pretty scandalous” for the day. But who was the father?

The answer to this question arrives when Greg sees old newspapers in the archives in Caernarfon, north Wales. These show one William Owen, a butcher, being chased for child maintenance payments. He also turns up in a 1901 news report of his being drunk in charge of a horse and cart – or, according to one witness, at the very least “more drunk than sober”.

William was raised by his maternal grandparents rather than his parents, but why? In Tremadog, William’s birthplace, Greg learns that William’s mother died shortly after her son was born. His farmer father, Evan Owen, left William with his in-laws.

Evan remarried, but his son seems never to have gone to live with him. Instead, Evan’s life revolved around a new family and religion, as a nonconformist chapel deacon. It’s difficult to know if father and son were in contact, but Evan would certainly have disapproved of Evan’s drinking.

Greg also learns how Evan met his end, after being thrown from a horse-drawn carriage into a flooded river. There’s even a ghost story associated with the incident.

Returning to William’s story, Greg heads for Porthmadog, to see the house where his grandmother was born. William, he learns, had two children by different women in the same year, 1907. One of these was a child by Martha Owen, who seems to have been William’s wife.

Yet more court records reveal that William still wasn’t paying maintenance to support his illegitimate daughters. By 1910, he owed £16, a debt that cost him 14 days in jail. Records also show that William moving south to work as a miner in the coal-mining town of Stanleytown.

It’s research that enables Greg to meet a “half great aunt” he never knew he had, Meirionwen, the last surviving daughter of William and Martha. From Meirionwen, Greg learns that William was a difficult man. At William’s grave, Greg feels little connection.

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For the final part of his journey, Greg heads north again, to see the family farm. He also learns that he can claim descent from Owain Gwynedd, the first Prince of Wales. Greg, surveying all he sees, quickly exclaims: “I rule this". At a local pub, though, everyone seems to claim a similar connection!

More seriously, as Greg reflects on research where the relationship between father and son has seemed central, he also muses on the “significance of extended family” and how this helps to shape us.

"I haven’t really worked out to what extent,” he says, “but I’ve felt [this] for the first time ever really.”