B is for... Brooke, Adelaide

Commander of the first manned settlement on the planet Mars - Bowie Base One. Captain Brooke headed an international team. She was a strict leader, showing little humour. She was particularly hard on her second-in-command - Ed Gold - but this was due to them previously having had a relationship.
The Doctor found himself visiting the base, and was horrified to find that the date was 21st November, 2059. He knew that this was the date when the base was destroyed in a nuclear blast, with the loss of all hands. The reason was never known, but Brooke must have activated the self-destruct sequence. The Doctor was determined to leave when it became clear that the crew were under attack from a water-borne parasitical organism. He admitted to Brooke that her grand-daughter would be inspired by her to become a space pioneer, and her descendants would have a significant role to play in intergalactic relations. Brooke told the Doctor of a childhood event - when she had witnessed the Dalek invasion after the Earth had been transported across space to the Medusa Cascade. Her father had gone out and left her, never to be seen again, but she had seen a Dalek outside her window. It had failed to kill her. The Doctor believed this might be because she formed a fixed point in time.
When he finally left the base, the Doctor decided that, as the last of the Time Lords, he no longer had to adhere to the Laws of Time. He would attempt to rescue as many of the crew as he could. Brooke was horrified, as this would mean the future he had described would never happen. She felt no-one should have the Doctor's powers. She went ahead and activated the self-destruct sequence to prevent the parasite from reaching the Earth. The Doctor took Adelaide back to her home on Earth. To keep history on track, however, she elected to shoot herself. History changed only in that she was recorded as having died on Earth, instead of on Mars.

Played by: Lindsay Duncan. Appearances: The Waters of Mars (2009).

• Amongst her many, many roles, Duncan voiced the protocol droid TC-14, seen at the beginning of The Phantom Menace.