Life on Mars' John Simm discovers dad wasn't his biological father on DNA Journey

John Simm has made a shocking discovery that his dad wasn’t his biological father.

The ‘Life On Mars’ star has been left stunned upon finding out the man who raised him, Ronald Simm, was not his real dad, during an appearance on ITV1 genealogy show 'DNA Journey', which he only took part in to support his friend and co-star Philip Glenister, 61.

On the programme, John took a DNA test and discovered the man who fathered him was called Terence Naylor, who died in 1998.

Speaking on the episode - which is airing on October 9 - the 54-year-old actor says: “The DNA results came back and my dad, is not my dad. It turns out he isn’t my biological father, which is a bit of a shock. It spun my world, and everything I thought I knew wasn’t real.”

John - who has kids Molly and Ryan with his wife actress Kate Magowan - used to sing and play guitar in pubs with Ronald, and now believes his real dad Terence could've even seen him perform one night.

He says: “The thing that blows my mind, he might have been in the same pub one night and watched me play.

“It’s one of those mad, ‘Back To The Future’, ‘Life On Mars’ things.”

The ‘Crime’ star also explains there was a short period of time between his mother Brenda’s breakup with Terence and getting together with Ronald, who passed away in 2015 aged 78.

John says: "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.”

The star admitted Brenda, 73, has been “absolutely floored” by the discovery.

What's more, John has also discovered he has a half-sister, Terence's daughter Karen, who he meets in the 'DNA Journey' episode.

The actor says: “I’m glad my dad isn’t alive to see this, because I’m sure he’d be shocked and upset.”