Racnoss invasion of Earth

The Racnoss invasion of Earth was an attempted invasion of Earth on 24 December 2007 by the Racnoss. (TV: The Runaway Bride)

Origins
The Racnoss were almost wiped out by the Fledgling Empires (TV: The Runaway Bride) and the Time Lords in the Racnoss Wars (AUDIO: Empire of the Racnoss) over 4.6 billion years BC. Nearly all of the survivors of the race escaped in their spacecraft, around which the planet Earth would later form. The Empress of the Racnoss stayed in her Webstar, but also went into hibernation at the edge of the universe until she decided to search for her young. (TV: The Runaway Bride)

Aftermath
Jack Harkness recalled that Harold Saxon first came to prominence when he had the Racnoss shot down, complimenting the Doctor on "nice work".

Following his election as British Prime Minister in 2008, Saxon, actually, cited the "the Christmas star that came to kill" as an example of an alien event which the British government failed to disclose to the public. (TV: The Sounds of Drums)

As a result of the Webstar's Christmas 2007 attack, combined with the appearance of the Sycorax spaceship above London on the Christmas before, London was deserted for Christmas in 2008. Two holdouts were Wilfred Mott and Queen Elizabeth II. (TV: Voyage of the Damned)

In a parallel world
In a parallel world in which Donna Noble never met the Doctor, and so was not present to convince him to flee after defeating the Empress of the Racnoss, he drowned when the Thames was drained into the abandoned Torchwood base, resulting in his death without regeneration. His body was retrieved by UNIT soldiers and the Doctor's TARDIS was salvaged from under the Thames, later being sent to a UNIT base in Leeds. (TV: Turn Left)