Rosamund 'Ros' Jane Pritchard is a supermarket manager who creates her own party, the Purple Democratic Alliance. Ros succeeds Tony Blair, having won the general election by a huge landslide. When she first comes to the job she knows nothing about politics, but with the help of her advisor Catherine Walker, who becomes Deputy Prime Minister and Chancellor of the Exchequer, she warms to the job, dealing with crises such as a plane exploding over Walthamstow and proposing a one-day-a-week car ban.