Rebel Queen, by Jane Robbins

We love the dumpy princess!

Her bridegroom, the Prince of Wales (later George IV), had to get drunk to go through with the marriage. Lord Holland described her as "an ugly mad woman", while the cartoonist George Cruikshank lampooned her as a blancmange with several chins. She flirted outrageously, ate raw onions and displayed an alarming taste in outfits when she tramped around Tunis in a short low-cut velvet dress, red-thigh boots, a wig and artificial eyebrows.

Caroline of Brunswick is remembered chiefly for her inflated vulgarity. In the thorough and well-argued Rebel Queen, however, Jane Robins focuses on her political significance. She tracks the events leading to Caroline's trial for adultery in 1820 and shows how it represented much more than a profligate monarch's attempt to ditch his repellent spouse. The case set the stage for political reform.

From the moment she touched English soil, Caroline was promoted by the press as a friendless, foreign bride shabbily treated by disdainful in-laws. She enjoyed the popularity that forever eluded her unlovable husband and became an unlikely figurehead uniting everyone disgruntled with the status quo, from those who simply detested George to rabble-rousers committed to social change. Over the years, Caroline took advice from unexpected quarters, including Alderman Matthew Wood, "London's high priest of radicalism", and William Cobbett, who published a controversial open letter to George IV explaining why the Queen was a radical.

With the population devouring the details of Caroline's "unbecoming and disgusting intimacy" with her Italian butler Pergami, the market for topical satire, cartoons and ballads mushroomed. Royalty was ridiculed as never before. Despite a punitive stamp duty, newspapers profited from the regal rumpus as circulations rocketed. The press increased its power by reflecting and shaping the opinions of a readership that had no other political voice.

Great Britain had been waging a costly war with France for 20 years. Peace, however, did not bring prosperity, and the lavish lifestyle of Prince George (now the Regent) proved especially galling. The nation expressed its discontent with the outdated parliamentary system and high unemployment by mass demonstrations, rallies and rioting. Both the Peterloo Massacre and the Cato Street Conspiracy took place against a background of repressive laws like the Six Acts, passed by a Tory government reliant on informers.

There's a good balance of gossipy detail and historical fact in Robins's account and she studs her prose with colourful quotations from contemporary diaries, newspapers and letters. She starts the story swiftly with the arrangements in 1794 for the marriage of the 26-year-old German princess to her first cousin. George, unfortunately, was massively in debt and already secretly and illegally wedded to the Catholic Maria Fitzherbert. On being introduced to gauche and garrulous Caroline three days before the nuptials, he looked ill and requested brandy. She, with her customary tactlessness, commented on his bulk. Nine months later, their daughter Charlotte was born. George then insisted on a separation, promising Caroline would never have to sleep with him again.

Caroline was banished to Blackheath; her access to her daughter was restricted. There were intimations of what was to come in 1820 with the Delicate Investigation of 1806. This enquiry was set up to establish whether there was truth in rumours that the estranged Caroline had borne an illegitimate son, conducted a lesbian dalliance and enjoyed the favours of various naval Captains.

The investigation yielded nothing but threw into Caroline's path a number of men who saw political advantage in defending her, and who would prove invaluable years later when she was on trial. Among them was the ambitious Whig politician Henry Brougham, whom Robins likens to a spin-doctor. He lobbied parliament on Caroline's behalf and stage-managed her public image as an injured wife. It was he who led her defence team brilliantly against the government.

Tired of her treatment in England, Caroline decamped abroad. She spent the years travelling, dancing with "indescribable abandon" and getting acquainted with the raven-haired Bartolomeo Pergami. So she might have continued, had Princess Charlotte not died in childbirth in 1817. George decided to sever ties with Caroline for good. His spies went into overdrive, with the Milan Commission amassing as much dirt on her as they could from anyone with information to sell - all of which could be used to help secure a divorce.

George's accession brought affairs to a head when Caroline insisted on returning. Her trial took the form of a Bill of Pains and Penalties. The lords would vote on whether or not Caroline had committed adultery; if so, they would strip her of her title and husband. The aristocracy may have sniggered at the dumpy 52-year-old, cheeks rouged, ostrich feathers bobbing in her hat, whose dirty linen was scrutinised by 300 peers of the realm - but they were fearful, too. As Robins points out, the country was edging closer to political convulsion than at any time since Charles I. The mob demanded a verdict of "not guilty". The popular cry of "No Queen, no King" resounded in the streets to the sound of smashing windows. Memories of intransigent monarchs and ministers violently dispatched were still fresh from across the Channel.

Robins devotes six detailed chapters to the trial with its touch of pantomime. Ballads cast Caroline as a virtuous paragon, "The Rose of Albion". Broadsheets hissed the witnesses - the "villainous" lower-class Italians who swore the queen fondled this or that part of Pergami, the faithless foreign maids weeping as they recalled stained sheets. In Brougham's capable hands the five-month trial switched from being about Caroline's innocence to whether the witnesses had been suborned.

Finally the bill was dropped. The débâcle continued into the following year with the undignified spectacle of Caroline arriving like the bad fairy at George's coronation in Westfirst from one door, then from another. That same day she fell ill with stomach pains and was dead within three weeks.

It would be tempting to portray Caroline as a proto-feminist heroine. Very sensibly Robins resists and remains even-handed, exposing the sentimental idolisation and political manipulation of this "people's princess" for what they were. But she concludes that the trial "demonstrated the strength and generality of support for change" and paved the way for the Great Reform Act of 1832.

Robins captures the vibrancy of a period in flux, perfectly illustrated by the behaviour of the people who lived through it. Who wouldn't admire the cool of the Duke of Wellington when asked whether he supported Caroline? Confronted by pickaxe-touting ruffians, he kept his sense of humour, replying "Well, gentlemen, since you will have it so, God save the Queen - and may all your wives be like her."