What's in a Name?
The episode was originally entitled The Final Days of Planet Earth. Writer Russell T Davies changed this when he saw it onscreen as somehow it didn't seem to 'fit'.
A bond of fate
Timothy Dalton appears as the Lord President of the Time Lords. This isn't the first time an actor who's played James Bond has appeared on Doctor Who. In the Sixth Doctor story, Trial of a Time Lord, the Valeyard was played by Michael Jayston who starred as 007 in a BBC radio production of You Only Live Twice.
The Doctor references Queen Elizabeth I who we last saw in The Shakespeare Code when she branded him her 'sworn enemy'. At that point the Doctor had no idea what he'd done to upset her... Elizabeth I also featured in the First Doctor adventure The Chase, back in 1965.
Murder most foul
At one stage writer Russell T Davies intended that the Master would kill several humans and leave a chilling 'M' at the scenes of their murder. This would form a macabre trail and provide clues for the Doctor, enabling him to locate his nemesis. But Russell realised this was unnecessary as it had been established that the Doctor would already 'know' where to find his fellow Time Lord and so the scene was cut.
Bid time return...
Flashbacks and the Master aside, this is the first time we've seen the mighty Time Lords for over twenty years. We first saw their home planet in the 1969 epic The War Games although we didn't learn it was called Gallifrey until Sarah Jane's first story - The Time Warrior.
Bid time return... (part two)
The episode features David Harewood as Joshua Naismith. We saw his character's surname in Planet of the Dead - an advertisement on the side of the bus contained the text, 'Neon by Naismith'.
So fair a cave
Some of the early scenes on the Ood's home planet were shot at Wookey Hole in Wells, Somerset. The Fourth Doctor story, The Revenge of the Cybermen, also featured scenes recorded at the Wookey Hole caves and the nearby cathedral in Wells featured in The Lazarus Experiment.