I didn't know much about life in the home office, which isn't surprising considering I'm an actress, so I asked around all my friends and friends of friends and eventually was introduced to a girl called Parna. We'd never met but she phoned and said I should meet her at her work and she'd show me around. I asked her where that was and she said "Number 10". She was working on Tony Blair's diary at the time, so that day I showed up and had the very good fortune to be taken around 10 Downing Street. I think that was the best research experience I've ever had! I based a lot of the character in the show on her.