Doctor Who: I rescued Kylie Minogue as David Tennant double

Saving Kylie Minogue from a bridge was not in Colum Sanson-Regan's plans when he turned up as a Doctor Who extra.

But David Tennant was not around, so someone had to do it, and producers thought Colum looked like the doctor.

"I've saved Kylie, flown the Tardis, held the screwdriver and had Billie Piper look deep into my eyes and tell me how much she loved me," joked Colum.

"I asked the producer 'Why am I putting on the doctor's suit? They replied 'Well, David Tennant isn't in'.

Now a father of two, Colum was earning some extra cash before his first child was born.

"I didn't know what was going on," recalled Colum of when he arrived on the set but was ushered past the "cold bus" where the extras usually hang around and was shown to a posh trailer.

The 10th Doctor had to leave the set for the 2007 Christmas special Voyage of the Damned, and producers needed a Tennant-alike for some extra shots showing his back.

So they improvised and Colum, then 31, stepped in to the suit synonymous with the Doctor since the world's longest running sci-fi TV show rebooted on the BBC in 2005.

Colum, now 46, had been asked by producers to be on set early but he had no inkling that his time (lord) had come.

"All of a sudden I was standing with the suit there, and I was handed a script and told 'You're gonna need this'," recalled Colum. "I was thinking pinch me, what's going on?

"Then I went for a haircut and a little Australian lady passed me dressed in a French maid outfit and said hello. I did a double take and realised I was there with Kylie Minogue."

The Australian singer and actor was a Doctor Who superfan and had asked for a part, which was humanoid waitress Astrid Peth, a one-off companion of the doctor.

"I was a bit star struck, for sure," he admitted.

His first work in Voyage of the Damned - where a starship replica of the Titanic is on collision course with Earth - was an action-packed scene where killer robot angels launched a deadly attack.

"There was a bridge, and the killer robot angels were trying to shoot, so I had to stop Kylie from falling over," recalled Colum.

"I had to hang on to her and pull her back from a precipice. That was the first thing I had to do in the morning."

The author and musician had a gig with his band that weekend in Leicester. As Kylie almost sang, he couldn't get it out of his head that he had worked with her - and we should all be so lucky.

"We got in the car and I said to my bandmates, guess who I've been working with this week?" said Colum, who lives near Cardiff.

"We'd been driving for almost two hours and had nearly hit Birmingham and they still hadn't guessed. I had to tell them! They're like 'absolutely no way'. It was so bizarre."

To Colum's pleasant surprise, producers were so happy with his work and lookalike skills, they asked him to play the Doctor again in the 2008 episode Journey's End - this time as his clone in the final episode of the fourth series.

That meant he had to be in the same scenes with Tennant, Billie Piper, John Barrowman and Catherine Tate, making her final appearance as a regular.

"I got to fly the Tardis in Journey's End," recalled Colum, who is originally from the Republic of Ireland.

"Everybody was gathered around the central console of the Tardis. We all had to have our hands on the machine and flying controls. Everybody was on that episode. There was a real buzz.

"I got to hold the screwdriver - they were very protective and kept taking it off me."

Colum was then involved in an emotional scene where Rose Tyler, played by Piper, had to say her final goodbyes to the doctor.

"It was an amazing and surreal experience.

"The nicest thing I have to take away was getting to work near David Tennant. I loved it. He was a thoroughly lovely, lovely guy and so professional. I think that was my favourite thing about the whole crazy time."

This weekend sees Tennant and Tate back together for Doctor Who, reprising their roles as the Doctor and Donna Noble in The Star Beast on BBC One on Saturday evening - but Colum will be back on his sofa with his family at home.

Husband to Kerry, singer and guitarist of band Goose, a creative writing lecturer and author of books like The Fly Guy, The Tall Owl and Other Stories, Colum has limited time for more extra work - especially after having his own trailer as the doctor's double.

"I'm looking forward to the show on Saturday with the return of some fantastic actors," added Colum.

"As a fan, working on the show was incredible and it's only strengthened my love for Doctor Who."