John Simm makes astonishing discovery about biological father in ITV's DNA Journey

Teaming up to find out more about their familial history, Simm discovers that the man he thought was his dad was not his biological father.

"It spun my world, and everything I thought I knew, wasn't real," says Simm. "It's turned out to be such a massive thing in my life and all I was doing was a favour for Phil Glenister so he didn't have to do it on his own."

In the first episode, which airs on ITV1 on Wednesday 9th October, Simm is followed on a journey as he discovers his new biological line and the story of his biological father who he never knew.

As he embarks on the journey, Simm recalls a conversation he had with his mother before taking the DNA test: "When they had me, in the '60s, they were both young…they were together and then they split up and were both with other people and then they got back together and then they had me. And I'd never heard this story before."

He explains that his parents had spoken to a doctor at the time: "And the doctor said, 'It's absolutely fine, the dates are fine.' But it turns out he isn't my biological father. Which is a bit of a shock."

Simm says that he considered pulling out of the film but decides to utilise the experts to find out about his biological father.

Throughout the episode, Simm and Glenister meet a club steward who tells Simm that his biological father lived above a working men's club with his parents.

"I can't get it out of my head, because we played this area in the '80s and he was here and he was in working men's clubs," he says.

"It's one of those mad, Back to the Future, Life on Mars things."

This journey culminates with Simm meeting his half-sister as she shares memories and videos of his biological father.

John Simm and Philip Glenister's DNA Journey with Ancestry airs on Wednesday 9th October at 9pm on ITV1, ITVX, STV and STV Player.

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