Kim Catrall was perfect
Kim Catrall is one of my least favorite actresses, in part because of her snooty nose in the air look, but in this film she was perfectly cast as the personal assistant of the former prime minister. She affected a snooty, cool efficient demeanor, but occasionally it slipped to reveal someone a little warmer underneath, particularly at the book launching when she explained that the intensive security was required by the Americans. She gave the impression of a fiercely ambitious social climbing snob and wannabe power broker whose path to the top is via the right beds, and who could maintain her cool no matter what.
Some viewers have speculated that she was also a CIA operative and was used to lure the Ghost to the launching, which she admitted was unusual as it was like inviting the mistress to wedding. This may be so. It is not always necessary to hit someone over the head with the obvious.