I just watched the last 3 eps in a row. Quite an epic indeed.
My only criticism was that I thought the Doctor's 'compassion' for the Master to be 'Over the top'. I believe the Master deserved to be punished for his evil deeds. The gutless Master chose suicide instead.
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wiki trivia:
In the episode's commentary, writer Russell T. Davies called the implication of Jack's nickname ("the Face of Boe") "a theory" as to the Face of Boe's origins, prompting Executive Producer Julie Gardner to urge him to "stop back-pedalling" about the two characters being the same. There was much laughter. Davies then mentioned the addition of a line in "Gridlock" in which the Face of Boe calls the Doctor "old friend", suggesting a strong connection between him and the Doctor. Jack previously referenced the Face of Boe in the Ninth Doctor Adventure The Stealers of Dreams, though the canonicity of spin-off material is unclear. Davies also jokingly termed the hand seen removing the Master's ring from the ashes of his funeral pyre "the hand of the Rani".[2]
The Master makes reference to the Sea Devils (which the Third Doctor and the Master encountered together in the 1972 serial The Sea Devils) and the Axons (which they met in 1971's The Claws of Axos).[3] The Doctor also makes references to the Daleks; the Daleks were previously seen to have dealings with the Master in Frontier in Space (1973) and in the 1996 Doctor Who TV movie.
Earth is referred to as Sol 3, the third planet from the star Sol, as it was in The Deadly Assassin.[3] Sol is the Latin name for the Sun, and is often used in science fiction.
The Master's laser screwdriver is said to be isomorphically controlled, a property the Doctor attributed to the TARDIS controls in Pyramids of Mars.
Clips from "Smith and Jones", "Utopia" and "The Sound of Drums" are used in this episode.
After receiving a great amount of psychic energy, and rejuvenating himself, the Doctor says the line: "I'm sorry, I'm so sorry", a frequently used catchphrase of his.
Martha mentions that she once met William Shakespeare ("The Shakespeare Code").
When the Master is shot by Lucy Saxon he says, "It's always the women." He was previously shot by Chantho in "Utopia".
The Doctor's severed hand from "The Christmas Invasion", "Utopia", "The Sound of Drums" and various Torchwood episodes can be seen at the end of the episode inside the TARDIS.
At the end of the episode, the Doctor says "What?!" three times, after the RMS Titanic crashes through the TARDIS wall, which is also his response to Donna at the end of "Doomsday", when she appears onboard the TARDIS.
This does not appear to be the Doctor's first encounter with the Titanic. In "The End of the World" the Ninth Doctor stated that he had been onboard an "unsinkable" ship and that he "ended up clinging to an iceberg". In "Rose", Clive shows Rose evidence that someone that looked like the Ninth Doctor prevented a family from boarding the ship. In The Invasion of Time, the Fourth Doctor assures Cardinal Borusa that he had nothing to do with the Titanic's demise. The Doctor has also been on the Titanic in novels (for example, the Seventh Doctor in the Virgin New Adventures The Left-Handed Hummingbird), but the canonicity of the novels is in question.
The hand seen picking up the Master's ring leaves open the possibility of reintroducing the character at a later date, although Russell T. Davies stated in the podcast for this episode that this would not occur in the 2008 series.[4]
Martha mentions that both UNIT and Torchwood have been studying Time Lords for several decades. Torchwood was set up in "Tooth and Claw" for the specific purpose of tracking the Doctor, while the Doctor worked for UNIT in the mid-20th century. During the Doctor's tenure with UNIT, a full season of stories revolved around the Master, ending in his capture by UNIT in The Dæmons.