Sylvia Brooke, the third Ranee of Sarawak, was mad, bad, and dangerous to know: a liar, racist, destructive mother, procurer and vetter of her husband’s women, a cock-tease self-styled as ‘frigid’ – in short, awful.

But if anyone deserves posthumous forgiveness, it is Sylvia Brooke. Consider her father, Reggie Brett. Seduced at Eton and himself a seducer of boys, he was in love with his own son. After a three-year romance with another Eton boy (Reggie was already a husband and father) he began writing letters, eventually thirty-five volumes of them bound in red leather, to his son, Maurice: ‘Still, I had seen you, Molly. Will you remember, years hence, how passionately you were beloved; with a real romantic passion which someday you may feel for someone else.’

Born in 1885, Sylvia described herself as ‘so ugly. And they kept telling me so’; she was like ‘an anaemic suet pudding’. Podgy, awkward, lonely, and suicidal as a child, Sylvia proposed to much older men, including G B Shaw and J M Barrie, who gently but flirtatiously turned her down. The morning after her wedding to Vyner Brooke, the third Rajah of Sarawak, ‘he looked at her, pulled a funny face and muttered “Well, that’s that then.”’ Or so she claimed, decades later, in her second autobiography.

That agonising little revelation may be a lie. But she also wrote, poor thing, ‘No one who has ever married has so hated the sleeping together more than either he or I did … as an act it is both ridiculous and awkward, and I take a very poor view of it indeed.’ I say poor thing, because after her marriage to her ever-adulterous Rajah, and until her death in 1971, Sylvia was almost never without a new or newish man at her side, most of them also damaged goods or just repulsive (and she may not have slept with any of them).

There are plenty of books about Sarawak and its ‘White Rajahs’, and why not? From the standpoint of the English public it was a weird place. Until 1946, when it was absorbed as Britain’s very last colony, it was a wholly owned or ‘free-lance’ monarchy, founded (or seized) by the ambitious adventurer James Brooke, the first Rajah. He was granted ‘Sarawak Proper’ by the Sultan of Brunei in 1841 and soon Britain recognised Sarawak as an independent territory. Inhabited by Dyaks, Malays and Chinese, its fame has endured because the Dyaks hunted heads. In 1946, two visiting MPs met some Dyaks who boasted that during the Japanese occupation ‘they lopped off 1,500 Japanese heads. One of them – which they wanted to present to us – was the head of the Japanese director of education … when it was alive it wore glasses. The Dyaks still kept the glasses on, and took them off every day to wipe them.’

The English public loved that kind of thing – at a distance – and Sylvia, who often affected Southeast Asian fancy dress, made much of ruling over such subjects. She made much, too, of how courteously the Rajah and Ranee treated every last Dyak, and how beloved the Brookes were in return, although for much of each year they were away in England. After the war an eagle-eyed visiting colonial officer noticed that the Brookes did ‘not seem to be interested in much beyond their own possessions and comfort. There must be something more, or perhaps was, in the past, to account for their great popularity.’ Sarawak was a genuinely happy place, he added, and ‘this atmosphere will be spoilt if a cold, hard, colonial system is substituted for the present happy go lucky but personal rule’. It was indeed personal: Vyner, a dotty, priapic, pathologically shy man, was genuinely interested in his subjects, spoke their languages, and deserved their love and respect. However, what Sylvia really liked was the adulation: ‘Perhaps I enjoyed more than I should have’, she admitted late in life, ‘seeing everyone rise to their feet as I entered a room, and the traffic drawing to one side as I went by.’ Noblesse oblige doesn’t do justice to her underlying contempt for her subjects. Education, she warned in 1939, meant that the white man was ‘no longer a synonym of mystery and law. Equality of race, familiarity of contact, have taken away power and put in its place a source of precocious liberty that has made the Dyaks and the Malays more difficult to control.’

But despite Vyner’s sensitive common touch, his judicial commissioner wrote in 1928 that it was ‘hardly true to say that the Rajah treats the natives as equals in society … he never includes them in the regular entertainments he gives to Europeans’. Indeed not. The most telling sentence in Eade’s book describes how at the Rajah’s balls in Kuching, Sarawak’s capital, ‘the Malay and Dyak mistresses of the European bachelor officers would sometimes climb into the trees in order to see how many dances their man was having with each white woman’.

Sylvia’s three daughters – she suffered for never bearing a son to succeed her husband – were rackety like their mother. They married eight men in total, including an all-in wrestler (‘the Gable of grapple’), were greedy but stupid about money, and were more or less encouraged in their idiocies by Sylvia, who for some years wanted the most outrageous of the girls to succeed to the title of Rajah.

I’ll say this for Sylvia: she could write. Always fabricating, she wrote a lot, made some money and gained what she really wanted – notoriety. She spent an evening in Hollywood, her ‘spiritual home’, with the dashing star Errol Flynn, who wanted to make a movie called ‘The White Rajah’. Sylvia wrote:

I waited; and suddenly the staircase became brilliantly floodlit. On it there appeared Errol Flynn himself in a pair of white close-fitting trousers that showed every nerve and muscle of his body. Slowly and gracefully he descended, giving me plenty of time to appreciate his entrance – and him. He flashed a smile at me that would have sent a thousand fans into hysterics … [Flynn’s wife] also wore white; a gorgeous creature, holding an enormous Persian cat in her arms. She greeted me briefly and proceeded to lie on the floor with her cat.

Too outrageous even for Sylvia, the film was never made.

Philip Eade has done yeoman research for this book, his labours extending to Sarawak and into mountains of letters, diaries, official documents, and many interviews. He quotes a couple of sources suggesting Sylvia was like the Mitfords or characters in Waugh. She wasn’t. Like them she had the unpleasant gift of the glittering, nasty putdown, but behind her flash there was little else. She may have been fun some of the time, but mostly she was sad, disappointed, conniving, or just silly. She described herself with deadly accuracy, and this is the side of her that Eade captures so well:

I found myself involved in illicit love affairs, family quarrels, faceslappings and brawls. It was like a madness; a touch of that same tropical fever we had all succumbed to in the Far East, and then recovered from, and now fell victim to again; a dangerous recklessness of heart that led to a dangerous recklessness of behaviour.