John Simm has been ‘left questioning everything’ after life-changing discovery on DNA series

Doctor Who actor John Simm has been left “questioning everything” after making a life-changing discovery on a DNA TV show.

The British star, known by many as The Master in the BBC’s long-running sci-fi series as well as DI Sam Tyler in Life on Mars , appeared on ITV ’s DNA Journey when he realised that the man he always thought was his father was not his biological parent.

Simm participated in the show alongside his Life on Mars co-star Philip Glenister, revealing he signed up so Glenister would not have to take part alone.

But it was Simm whose life has been most altered by the series after being told that his true biological father was not Ronald Simm, as he believed, but a man called Terry Smith.

Speaking on the episode, as reported by MailOnline , Simm said: “It’s turned out to be such a massive thing in my life and all I was doing was a favour for Phil so he didn’t have to do it on his own. It’s spun my world... everything I thought I knew wasn’t real.”

The Grace actor considered quitting the show after making the discovery but decided to use the experts for information on his real father.

In the episode, Simm learnt that Smith is dead, but is told he used to frequent the same working men’s clubs as Ronald, a musician who died in 2015.

He said: “The thing that blows my mind is me and my dad played [gigs] around here loads of times. We definitely played here a lot and he might have been in the same pub one night and watched me play.

“I can’t get it out of my head because we played this area in the 1980s and he was here – he was working in men’s clubs. It’s one of those mad Back to the Future - Life on Mars things.”

Simm then revealed a chat he had with his mother before filming the show that took on new light after his astonishing discovery: “When they had me, in the 1960s, 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.”

Simm and Glenister’s episode of DNA Journey airs on 9 October. Simm will be playing Scrooge in The Old Vic’s production of A Christmas Carol , from 11 November to 6 January.