After 200 years under lock and key in the royal inner sanctum, all the letters, diaries and family documents of one of our most important monarchs are finally about to emerge from the vaults. Documentary film-makers, who were granted extensive access to the Royal Archives deep inside Windsor Castle for the first time, have produced a historic film for BBC Two which sheds a fascinating new light on George III, Britain's longest ever reigning king. In an unprecedented royal project, historians and archivists are preparing all of the King's and his family's personal papers - hundreds of thousands of them - for public consumption online. George III may be chiefly remembered for his madness, but this astonishing, unseen collection reveals a pivotal monarch driven - and occasionally driven to distraction - by his duty and his family; a political micro-manager and a restless patron of science and the arts; an obsessive traveller who never left southern England yet toured the world in his mind through emissaries like Captain Cook; a sovereign who was determined to be different. Simon Callow and Sian Thomas are the voices of King George and Queen Charlotte.