Fire Trap

On Christmas Day, 2006, the Sycorax came to Earth in a spaceship. It was later destroyed by Torchwood on the command order of then-Prime Minister Harriet Jones with a laser taken from scavenged alien technology. The Tenth Doctor immediately chastised her for this immoral act, seeing it as murder. When Harriet disagreed with the Doctor, calling it an act done to protect humanity from further attack, he brought down her government with a subtle push that snowballed into her removal from power. (TV: The Christmas Invasion) After the destruction of the spaceship, UNIT officers were given a directive from the PM's office that the ship blew up of its own accord, despite that not being the case. (PROSE: Project Rooftop)

Martha Jones believed that Saxon had been responsible for shooting down the ship, which she described as "that big alien deathstar thing". (PROSE: Martha Jones' MySpace blog)

Behind the scenes
According to the non-narrative based work Doctor Who: The Visual Dictionary, Fire Trap was the name of the asteroid on which the Sycorax originated. It was located in the JX82 system and consisted mostly of rock and ice, with very little in the way of natural resources such as metals. The tribes lived just below the surface of the asteroid. When an unidentified spaceship collided with the asteroid, the Sycorax stole its engines and fitted them into the asteroid to use as a spaceship.