George IV was larger than life. A gambler and a drunkard, he married a widow older than himself, illegally and in secret, dabbled in the politics of opposition and amassed fantastic levels of debt. His legitimate union with Caroline of Brunswick ended in an acrimonious and lengthy divorce; all the while mistress followed mistress, each one seemingly fatter and greedier than the last. He was a gift to cartoonists, but had the misfortune to live during the golden age of their art. The merciless lampoons of Gillray and the Cruikshanks, drawn mainly from Kenneth Baker's unique collection, make many of today's cartoons seem almost respectful.

Yet, in fact, as Kenneth Baker asks, was George really a Cad, or a Catalyst? As Prince Regent during George III's last illness he gave his title to an elegant style of architecture and design. He was London's best town-planner - with legacies that include Regents Park, Regent Street, Waterloo Place, Trafalgar Square and the National Gallery, and - outside London - the Brighton Pavilion and a modernized Windsor Castle.

George acquired for the Royal Collection works by all the best artists of the day, as well as by such masters as Rembrandt and Rubens, making it one of the finest collections in the world. He also kept copies of Jane Austen's novels in each of his houses.

George faced four major political crises as Regent and King, and his handling of these - so different from his predecessors - paved the way for today's constitutional monarchy. George loved appearing in public and organized splendid celebrations open to ordinary men and women, such as his coronation, and he invented the state visit. By the time of his death the monarchy had become less mysterious, distant and secret.

Kenneth Baker draws on a lifetime's experience of high politics to scrutinize the changing figure of George, setting his extraordinary life in the context of the French Revolution, the Napoleonic Wars, the Peterloo Massacre, Wellington, Pitt and Fox, providing a skilful and thoroughly enjoyable understanding of the period's most colourful character.