Alistair Lexden is the Conservative Party’s official historian.  His publications include a study of the Primrose League, the organisation which ensured Disraeli’s political immortality.

They first met in April 1832 during the closing stages of the crisis over the Great Reform Bill at a party given by Bulwer Lytton, at that point a rather more successful novelist than Disraeli, and his highly unstable wife Rosina, who was a close friend of Mary Anne Lewis, as she then was, an attractive and extremely flirtatious woman.

She was married to a rich but wholly undistinguished Tory MP, Wyndham Lewis, who bought himself seats in Parliament, brazenly making payments to voters. The Lyttons, their hosts for the evening, later fell out spectacularly. She took to making dramatic appearances during election campaigns in the 1850s, accusing Disraeli of having sex with her husband when both men were beginning ministerial careers.

The social circles in which the widely derided writer who was to become a great Tory statesman and his rackety future wife encountered each other were, even by the standards of the day, colourful and raucous. It was not love at first sight.  Initially, Disraeli was unimpressed by his new acquaintance. He described her to his devoted sister, Sarah, as “a pretty little woman, a flirt and a rattle; indeed gifted with a volubility I should think unequalled, and of which I can convey no idea. She told me that she liked silent, melancholy men. I answered that I had no doubt of it”.

She was twelve years older than him, but that does not seems to have concerned him much. He was never attracted by bright young things (except where his own sex was concerned).  She retained immense vivacity and dressed with a flashiness that turned heads, always displaying a fine array of diamonds. She was to toy with the hearts of many admirers (not entirely chastely) before finally settling for Dizzy, as she almost invariably called him (shortened sometimes to Diz), in 1839, less than a year after her first husband’s sudden death from a heart attack.

By then Disraeli had come to enjoy her high-spirited company. She canvassed merrily and tirelessly in Maidstone, an extremely corrupt two-member seat, for which Dizzy and Wyndham Lewis were elected in 1837, incurring enormous expenses which she eventually paid. Daisy Hay, who teaches English at Exeter University (and refers to herself as a BBC New Generation Thinker, whatever that may be), describes the boisterous campaign: “ Mary Anne adorned herself, the candidates and their carriages with purple ribbons and made friends with every voter she met, spending the canvass, as she told John [her black sheep of a brother] in a ‘tumult of joy & bustle” ‘.

She showed the same exuberance in Shrewsbury, which Disraeli represented in the 1840s. On one occasion he visited the town without her. He wrote to tell her that “wherever I go, I hear nothing but Mrs Disraeli & why did she not come. Among the shopkeepers, whom I wish most to please, your name & memory are most lively & influential”. She was the first Tory woman to take to electioneering with relish and enthusiasm, setting an example that thousands of her sex would follow in the late nineteenth century as members of the Primrose League, the first great Tory mass movement, established in her husband’s memory.

There was never a dull moment. They slept together before their wedding at the mansion overlooking Park Lane which she inherited after Wyndham Lewis’s death. “Love-making after marriage”, she wrote, “is the best way of reconciling me to love-making before”. Leaving hurriedly to get down to Westminster, he forgot to take his watch and seal; she posted them on to him. There were rows and tantrums. In a furious letter he threatened to end the affair, telling her that in the years to come “you will recall to your memory the passionate heart you have forfeited, and the genius you have betrayed”. In calmer moments he sent her dreadful doggerel verses, including one about “poor Diz/ With a second rate phiz/ and all I can do/Is to love you most true”. Passion occasionally reduced even this great master of the English language, one of the most eloquent men of his age, to pitiful banality.

The best-known fact about this remarkable marriage is that Disraeli was after her money. He had mountainous debts (over a million in today’s values) which derived chiefly from madcap investments in the 1820s in South American mines, which turned out to be non-existent. This future Chancellor of the Exchequer went in constant fear of writs from his creditors whenever Parliament was dissolved for a general election.

Wisely, he withheld the full details of his parlous financial condition from her. But he always managed to enlist her help when any angry duns threatened to come calling. He told her candidly that “when I first made my advances to you, I was influenced by no romantic feelings”, but denied that he had had an eye on her wealth, adding amazingly that her fortune “proved to be much less than I, or the world, imagined”. In any case, he went on, romantic feelings soon overwhelmed him. “I felt that my heart was inextricably engaged to you” and “from that moment I devoted to you all the passion of my being”. The shrewd woman was under no illusions. “Dizzy married me for my money”, she would say in later years, “but he would do it again for love”.

In 1868 she was made a peeress in her own right and became Viscountess Beaconsfield (his Earldom came eight years later after her death at the age of 80). A sharp-eyed observer watched them closely at a service in St Paul’s. Disraeli “was clad in a garment which, I believe, he greatly affects – a long white coat, designed, possibly, to assist the curious eye in its search for him. He was paying his wife, Lady Beaconsfield, a degree of attention so unusual in public, and so very unusual in church, as to suggest to the cynical observer that it could scarcely always be maintained in the same perfection under the accomplished gentleman’s roof”. Here the editor of the journal in which it was later published interjected sharply: “Dizzy’s devotion to his wife was perfectly genuine”. She basked in his political triumphs and would have loved the way in which the piece concluded: “For every opera-glass which was bent on Gladstone at St Paul’s, I am sure that a dozen were turned on Dizzy”.

Disraeli always had handsome young men in his life. He wrote love letters to at least one of them. Increasingly, his biographers today speculate about whether these relationships had a sexual element. What was the truth about the lurid allegations made to bemused voters by Rosina Lyttton, at whose party the Disraelis first met? Daisy Hay writes very oddly about them: “ the question of whether he [Disraeli ] and Bulwer had a sexual relationship is anachronistic, since it relates to a period when male sexuality was less rigorously categorised”. She evades the issue.

Whatever the truth, the Disraelis’ happiness together was complete. Mary Anne once told Queen Victoria that she always slept with her arms around her husband’s neck. The royal reaction is unrecorded, but it is unlikely to have been unfavourable in view of her own passionate devotion to Prince Albert. Many grand contemporaries ridiculed her for her tactless remarks and thought her stupid. They were wrong.

Could there be anything more moving than Mary Anne’s own words in a letter which she wrote for him to open on her death? “And now God bless you, and comfort you, my kindest dearest – you have been a perfect husband to me, be put by my side in the same grave. And now farewell my dear Dizzy, do not live alone, dearest, someone I earnestly hope you may find as attached to you as your devoted Mary Anne”. The letter was placed next to his heart in their shared vault at Hughenden.

This book tells an extraordinary love story, and tells it wonderfully well.

Mr and Mrs Disraeli: A Strange Romance by Daisy Hay is published by Chatto & Windus, £20.