Speaking to SFX, he teased: “It will be as Christmassy as Hell. I might be cleverly redeploying a known Christmas story again, sort of… but probably not the one you think!”

The writer added: “It will be massively Christmassy and moving and sentimental and sweet. It’ll be set partly on Earth, but not completely. And it might have a period setting…”

2010’s Christmas special, ‘A Christmas Carol’, starred Harry Potter actor Michael Gambon and opera diva Katherine Jenkins in her first acting role.

Last week Moffat revealed that his plans for the show’s 50th anniversary in 2013 are “quite extensive and changing all the time”, promising that “it’ll be amazing”.

The second half of Series 6 kicks off with Moffat’s ‘Let’s Kill Hitler’ on Saturday 27th August.

> Buy the Series 6 Part 1 DVD on Amazon.

> Buy the Series 6 Part 1 Blu-ray on Amazon.

Watch the BBC’s latest Series 6 Part 2 trailer, featuring footage from the six remaining episodes of the series…