Trivia: Possible Spoiler: At the time of this writing, it is generally believed that the "Mister Saxon" referred to throughout Season 3 will turn out to be The Master. One piece of evidence backing this theory is The Master's penchant for anagrammatic aliases: Mister Saxon is an anagram of "Master No Six," and if it's true, John Simm would be the 6th actor to play The Master. [Russell T Davies (who wrote most of the episodes) has said that the anagram is pure coincidence which was picked up by some people, but was completely unintended. Still interesting regardless.]
Trivia: Jack causes the Clock Tower to light up. At the end, the writer wanted someone to say 'Jack, did you remember to turn off Big Ben?' then have a bomb land on the Houses of Parliament and the Clock Tower. (The Houses of Parliament did get bombed. The joke was to make it all Jack's fault).
Trivia: Freema Agyeman, who later played Martha Jones, plays Adeola in this episode. Russell T Davies later said that by the time he came on set and saw her performance, she had already shot her death scene - if she hadn't, he would have rewritten the episode so that she survived to become the next companion. Hence why Martha references her cousin Adeola in "Smith and Jones."