Doctor Who guest star never filmed with David Tennant, Catherine Tate

The scene saw the Doctor and Donna land in Newton's apple tree, and make a joke about gravity - something which Newton mishears as 'mavity', leading to a running joke throughout the episode where the word appears to have been permanently changed.

However, it turns out that despite their characters exchanging dialogue, Curtis never actually shot with David Tennant and Catherine Tate, with their sections of the scene being filmed separately, in different times and different locations.

Steffan Powell revealed this in the latest episode of Doctor Who: Unleashed, in which he said: "Sometimes, usually because of a clash with timings, actors can be in the very same scene together, without ever actually coming face to face."

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He continued: "When it came to filming the Isaac Newton scene in this special, Nathaniel Curtis, who plays the great man himself, was in a walled garden on the Welsh coast, when he was rudely interrupted by a low-flying TARDIS.

"Except the TARDIS, and its occupants, weren't in Isaac Newton's tree. The tree was empty. They were 25 miles away in Cardiff Bay, filming on a different day."

It was then revealed that while Curtis spoke to an empty tree for his scenes, Tennant and Tate filmed theirs against a blue screen.

In the episode of Unleashed, Tennant said: "It's a shame, because I've met Nathaniel and he's really nice, and I would have liked to have a little scene with him."

Tate added: "I would have liked to have met him, I've not met him."

Tennant then joked: "But apparently he asked not to have anything to do with us. He asked to be kept apart, he was very particular. He accepted the part on that very strict condition."

However, Curtis said: "I mean, I love David Tennant. I love David Tennant. A, he's such a lovely man, and B, he's a brilliant Doctor. And I grew up watching David Tennant as the Doctor, so I think that it's a bit surreal, to be honest."

Doctor Who's third 60th anniversary special The Giggle airs at 6:30pm on Saturday 9th December on BBC One and BBC iPlayer. Previous episodes are available on BBC iPlayer and on BritBox – you can sign up for a 7-day free trial here.

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