WHITEHALL - the name of a street now synonymous with the civil service - has been the centre of British religious and political power for over 500 years. Whitehall takes the reader behind closed doors to explore the fascinating history that lies behind the fa ade of the great departments of state and some of the greatest figures in British history, including Henry Vlll's playground, the execution of Charles I, Nelson's tortured love life, and Winston Churchill's plans for a last stand against the forces of Hitler's Nazi invaders. It explores the private house in Whitehall - ignored by tourists today - which became the most notorious address in London, when Byron and Lady Caroline Lamb conducted their very public and tempestuous love affair there. Inside Admiralty House, screened from public view, is the elablorately decorated boardroom equipped with its own wind clock where Nelson received his orders to attack the French. There is also the dining room where Nelson fumed over dinner with his wife Fanny, who burst into tears at his black mood. Fragments of the tennis courts where Anne Boleyn watched Henry Vlll playing tennis in his 'slops' have survived behind the walls of the Cabinet Office at 70 Whitehall. Beyond its glass doors, a secret passageway leads to Number Ten Downing Street. Cabinet papers reveal that Winston Churchill planned to use Whitehall as a 'fortress' in 1940 when Britain faced imminent invasion by Hitler's Nazi forces. The documents published for the first time show how Churchill prepared for street fighting in Whitehall's departments, as he made his final stand. And it also reveals for the first time the films that helped Churchill escape the rigors of war in his underground cinema at Whitehall as the Prime Minister battled to preserve Britain for another 1,000 years.