Few figures in British history have been so deeply and so consequentially involved with the British royal family as Winston Spencer Churchill.

While numerous men of stature have advised kings and queens during their reigns, Churchill is unique in his role: helping to shape not only a reign, but an entire royal dynasty. However, it was by no means a seamless relationship. At times, the royal family treated him with suspicion and contempt; at others, their relations were avuncular, competitive and cheering. Yet whether he was playing the role of antagonist to the royal family or that of trusted confidante, Churchill's influence was central to the twentieth-century history of the British monarchy.

The attitudes of the royal family towards him, whether warm or icy, were also crucial in creating the legend of Winston Churchill. The House of Windsor helped shape his career and his legacy: from his young days receiving paternal advice from Edward VII; his middle years of diehard loyalty to King Edward VIII during the abdication crisis; his initially grudging but ultimately fruitful partnership with George VI during World War II; to his enduring fondness for young Elizabeth, the last sovereign he served.

While there have been many biographies of Winston Churchill on the one hand, and many volumes on members of the royal family on the other, none of these has yet charted the relationship between Churchill and the royal family itself, even though these partnerships shaped and defined the House of Windsor and modern Britain. In short, the history of the monarchy in the twentieth century cannot be fully understood without reference to Winston Churchill, and Churchill's life and legacy cannot be adequately appreciated without accounting for his relationship with the royal family.

Having unearthed much under-appreciated material relating to Churchill held in the Churchill Archives at Cambridge University - including diary entries, postcards, and letters to and from kings, queens and princes - Andrew Morton presents a meticulously researched dual biography of Winston Churchill and the House of Windsor. It is a drama of the first order. At times thrilling and always compelling: this is the saga of a man, a family, a beloved institution, and a regal dynasty.