In Voyage of the Damned episode of Doctor Who (2005), the Nuclear Storm Drive of the Titanic was capable of destroying all life on the planet.
From the transcript:
The Doctor: Oh, yes. If we hit the planet, the Nuclear Storm explodes and wipes out life on Earth. Midshipman, I need you to fire up the engine containment field and feed it back into the core.
Conversation with Capricorn:
Capricorn: I have men waiting to retrieve me from the ruins and enough off-world accounts to retire me to the beaches of Penhaxico Two, where the ladies, so I'm told, are very fond of metal.
The Doctor: So that's the plan. A retirement plan. Two thousand people on this ship, six billion underneath us, all of them slaughtered, and why? Because Max Capricorn is a loser.
In a later episode Turn Left, Donna was pushed into an alternate timeline by a fortune teller in which she never met The Doctor. Due to this, The Doctor died. Without him, the Titanic crashed into Buckingham Palace, which destroyed London. Why did it destroy London only?
Is this a known plot hole? Or I am missing something?