Andrew Roberts, one of Britain's premier historians, overturns the received wisdom on George III

George III, Britain's longest-reigning king, has gone down in history as 'the cruellest tyrant of this age' (Thomas Paine, eighteenth century), 'a sovereign who inflicted more profound and enduring injuries upon this country than any other modern English king' (W.E.H. Lecky, nineteenth century), 'one of England's most disastrous kings' (J.H. Plumb, twentieth century) and as the pompous monarch of the musical Hamilton (twenty-first century).

Andrew Roberts's magnificent new biography takes entirely the opposite view. It portrays George as intelligent, benevolent, scrupulously devoted to the constitution of his country and (as head of government as well as head of state) navigating the turbulence of eighteenth-century politics with a strong sense of honour and duty. He was a devoted husband and family man, a great patron of the arts and sciences, keen to advance Britain's agricultural capacity ('Farmer George') and determined that her horizons should be global. He could be stubborn and self-righteous, but he was also brave, brushing aside numerous assassination attempts, galvanising his ministers and generals at moments of crisis and stoical in the face of his descent - five times during his life - into a horrifying loss of mind.

The book gives a detailed, revisionist account of the American Revolutionary War, persuasively taking apart a significant proportion of the Declaration of Independence, which Roberts shows to be largely Jeffersonian propaganda. In a later war, he describes how George's support for William Pitt was crucial in the battle against Napoleon. And he makes a convincing, modern diagnosis of George's terrible malady, very different to the widely accepted medical view and to popular portrayals.

Roberts writes, 'the people who knew George III best loved him the most', and that far from being a tyrant or incompetent, George III was one of our most admirable monarchs. The diarist Fanny Burney, who spent four years at his court and saw him often, wrote 'A noble sovereign this is, and when justice is done to him, he will be as such acknowledged'. In presenting this fresh view of Britain's most misunderstood monarch, George III shows one of Britain's premier historians at his sparkling best.