Three-part series by Michael Cockerell starts with the role played over the years by the most powerful unelected member of the government, the Cabinet Secretary. He is the real life Sir Humphrey from Yes Prime Minister, who rules the civil service from Whitehall's least understood ministry, the Cabinet Office. Mixing rare archive with candid interviews, the programme tells the story of the many battles for power between Britain's top civil servant and their prime ministers.

Michael Cockerell reveals what life has really been like over the years in 10 Downing Street. Insiders talk candidly about the constant battles and the tragicomic events behind the famous black door. The film shows what an unlikely place No.10 is to run a government from.

Michael Cockerell reveals what really happens in the hidden power houses of Whitehall, the cabinet minister's private office. These are where political advisers have bloody battles with civil servants for the hearts and minds of their ministers, from where gaffes are averted and plots hatched. Mixing rare archive with candid interviews, the programme tells the story of what goes on within this most influential of secret networks.