Doctor Who icon reveals her and William Hartnell's own alternative backstory for the Doctor and Susan

Doctor Who has seen countless writers across its 62-year history – but now it's been revealed that even its original stars, William Hartnell and Carole Ann Ford gave it a go!

Ford, who played the first ever companion Susan Foreman, has revealed that she and Hartnell, who starred as the first incarnation of the Time Lord, invented a backstory to explain how the Doctor's travels began, before the first ever serial An Unearthly Child.

Speaking exclusively to RadioTimes.com, Ford recalled that the pair were "never given any" backstory – so felt they should fill in the gaps!

"Bill and I put our heads together and we made it up," she revealed. "We thought that the most likely thing was that the TARDIS was not this year's model. It was a previous model which had been tarted up a bit, and the tarted up bits weren't quite working as smoothly as they should have done.

"So Bill, my grandfather, was in a huge sort of aircraft hangar-type place with loads and loads and loads of other TARDISes, all being tinkered with. And he was tinkering away with it and making everything work more smoothly, when suddenly there was an invasion from another planet.

"Everybody was going crazy, and he just bundled me into the TARDIS and said, 'Right, we're out of here.' So we got in with only a partially-working TARDIS, which he continued to fiddle with throughout the series, and finished up where we finished up – Totter's Lane."

Speaking about the importance of having a backstory to work with, Ford added: "An actor has to have an idea of what happened before you stepped through the door, and also what's going to happen after you step through the other door."

During the in-depth interview, Ford also reflected on her friendship with Hartnell, including her first impressions of the actor.

"I thought he was adorable!" she said. "He was very charming, very sweet, very considerate, and took it all very seriously, which I approved of. I don't like people messing about and giggling – they've got to take the work seriously."

She added: "The part was so important to him. It was everything to him. And because of that, he was a real perfectionist with it.

"I think if people were a little bit off about the idea of Bill, it may be because he was such a perfectionist, and if he saw people fooling around with the part, not taking it all seriously... but he was right.

"Unless you're doing it seriously, it doesn't mean anything to the audience. If you're thinking, 'Oh, a load of rubbish', then how are the audience going to ever accept what's going on and be entertained by it?

"We got rid of all our giggles about the various monsters in rehearsals, and just as well we did, because sometimes I look back and I think, 'How did I ever keep a straight face?!'"

Carole Ann Ford's full interview will be available on RadioTimes.com soon.

Missing Doctor Who? Register now for Radio Times's Doctor Who Insiders club for exclusive interviews with Doctor Who legends every month.

Check out more of our Sci-fi coverage or visit our TV Guide and Streaming Guide to find out what's on. For more TV recommendations and reviews, listen to The Radio Times Podcast.