Factual error: Colonel Mace says the Sontaran ship is orbiting 5,000 miles (8,050 km) above the Earth. However, in shots of and from the ship in both this episode and "The Sontaran Stratagem", the Earth appears far too small for the ship to be that close, with the ship's true distance appearing to be well over double that. (00:08:34)
Factual error: The Doctor sets the atmosphere on fire, but only the upper part burns. The atmosphere extends from the Earth's surface (where it is densest) upwards, and so the flames would come right down to the ground, burning everyone to death. Of course that wouldn't work with the plot, so artistic licence has been applied.
The Unicorn and the Wasp - S4-E7
Factual error: The hotel in Harrogate was not called the Harrogate Hotel as shown in the episode; it was called the Swan Hydropathic Hotel.
The Unicorn and the Wasp - S4-E7
Factual error: In Lady Edison's flashback, she's reading "The Murder Of Roger Ackroyd", her favorite book. However, this episode is set in 1926, and the dust cover is from 2006.
The Unicorn and the Wasp - S4-E7
Factual error: In real life, Agatha Christie's famous disappearance occurred in December 1926. This episode is quite plainly not set in winter, what with the outdoor garden party and lush green foliage.
Factual error: During the climax, the Moon is visible in the background, and is depicted as full. On December 24, 1851 in real life, the Moon was at first quarter phase.
Factual error: When the Immortality Gate is activated, there's a wide shot of Earth as the wave from the device goes around the planet. In another instance of a mistake made by a few previous Christmas specials, despite this taking place on Christmas Day, the North Pole is looking very, very sunny for what's supposed to be the dead of winter. (00:54:50)
Factual error: When the shot zooms out from Earth across the Solar System before revealing the narrator, Jupiter and Saturn are shown. Although scaling is somewhat exaggerated, Saturn appears to be closer to the Sun than Jupiter, which it most definitely is not in real life. (00:57:57)
The End of Time: Part Two - S4-E18
Factual error: The Vinvocci ship is said to be orbiting 100,000 miles above Earth, later refined to 105,000 miles. That's one-third of the distance to the Moon, and the Earth's apparent size from the windows of the ship is far too large for them to be that distance, or even 100,000 kilometres above the Earth's surface. Judging by the Earth's apparent size, the spaceship is actually orbiting 6,000-7,000 kilometres above the planet's surface.
Chosen answer: No, no information is avalible for the identity of the entity.
Repo_Man