1. The Baker Street Irregulars
Major Palmer is described by the Doctor as one of the “Baker Street Irregulars”, in this case indicating he was part of Churchill’s Special Operations Executive, which conducted espionage, sabotage and reconnaissance against Britain’s enemies. For more information, see the BBC’s history website.
Given his age in 1974, he must have been very young to send other operatives to their deaths during the war, as he states here.
2. You say Metebelis, I say Metebelis
The planet Metebelis Three, and the mind-focussing powers of its crystalline substances, formed vital plot points in 1973’s The Green Death and 1974’s Planet of the Spiders, making its first appearance in Doctor Who contemporaneous with the setting of this episode.
Of course, back then the Doctor pronounced it differently – MeteBEElis rather than, as here, MeTEBBelis. It does seem odd that the production team would include a deliberate back-reference to Classic Who and yet not pick up on the apparent discrepancy.
But then again, maybe it was the Third Doctor who got it wrong in the first place. Also in The Green Death, he mispronounced the word “chitin” as “CHITTIN”, rather than the correct “KITE-IN”. Which precipitated a famous letter to the production team of the day:
The reason I’m writin’
Is how to say “chitin”
Perhaps Matt Smith took elocution lessons from Siri? This is how Apple’s UK voice (based on Jon Briggs, voiceover artist for The Weakest Link and other shows) pronounces it.