In this book on the eighteenth-century designer William Kent, Tim Mowl recalls how he ‘outed’ Horace Walpole in a lecture to the Georgian Group: ‘A number of ladies walked out in protest. It was not just a matter of “no sex please, we’re Georgians”’ he writes ‘but also one of “let us have no sharp, realistic standards of appreciation of the true, coarse tone of the period”.’

That lecture is now a legend in architectural history circles. ‘What do you remember?’ I asked someone who was there. ‘One or two people definitely walked out. Maybe three. But it was a lunchtime lecture and at least one was nipping out to get a sandwich.’

Whoever walked out and for whatever reason, this is a book on the rebound. The trauma has given an irresistible energy to Mowl’s reappraisal of Kent’s life as a designer of houses, gardens and furniture. He believes that modern scholarship has a ‘sugary reverence’ for the period, placing Kent’s work in a polite world of classical harmonies, harpsichords and porcelain; and that the idea of the Age of Reason is an ‘academic conspiracy’. For him, Kent was a ‘clown of lively genius’ who thrived in a world of quarrelling princes, corrupt courtiers, sex, debtors’ prisons, bassoons, smallpox, and more sex.

Kent was born in 1685, the son of a joiner in Bridlington in Yorkshire. His great patron, Lord Burlington, grew up twenty miles away. Visiting the town of Bridlington, Mowl listens to two old men talking in their local café. What, he wonders, was the true sound of his characters in an age before received pronunciation?

Burlington: Oo ee, that Alexander Pope a says to aye
Kent: Never i this world tha don’t say.

Sic. Certainly, Lord Burlington – who gave his name to the swanky Arcade in Piccadilly, those expensive socks, and a smart dry-cleaner’s in Kensington – will never seem quite the same again.

The young Kent’s talent as a painter was spotted by several of the local gentry, who clubbed together to send him to study in Rome. He stayed for nine years, and painted the ceiling of the Church of San Giuliano dei Fiamminghi – an exceptional commission for a young Protestant and a foreigner. But his genius was not as a painter, in part – it is explained – because of his misguided admiration for Correggio’s frescoes in the dome at Parma: ‘a terrible tangle of bare flesh and soft porn … a disaster of a composition’.

It was in Italy that Kent met Burlington, and in 1718 he returned to London in his retinue of nine carriages. The next year Burlington led a palace coup. The great Sir James Thornhill was unseated from his commission to paint the ceilings of Kensington Palace and replaced by the new protégé. It was the first victory in Burlington’s campaign to transform British taste. The trouble was, says Mowl, that Burlington’s taste was ignorant.

The book’s agenda is to show that Kent was the greatest designer of the century – greater than Adam – but that his imagination was suppressed by Burlington and his circle. Alexander Pope is one villain: ‘the most appalling scrounger and ingratiating creep’. Another was the architect Colen Campbell, whose Vitruvius Britannicus began the Palladian Revival: ‘a rogue … a charlatan … one of the most malign influences ever to work in British architecture’. These men imposed on Britain a dull and boxy architecture for ‘nervous pedants … [with] a lurking puritan conscience’. They called their new style ‘Palladian’ but they misunderstood Palladio.

Pope and Campbell had never been to Italy, and Burlington only spent a single day in Palladio’s Vicenza. The city was flooded, and he had to sleep in a chair. In consequence, he saw just three of the master’s designs – and failed to grasp that Palladio’s architecture was much more than the mathematics of proportion. In the rain and hurry, he did not appreciate its sensuous play of light, colour, and views of landscape.

A second vignette from that same year of 1718 conjures up what might have been. The Prince of Wales – the future George II – and his cosmopolitan wife Caroline of Ansbach established their court at a villa beside the Thames at Richmond. Guests flitted between the lamp-lit avenues of trees, and water music played from gondolas. And that year, too, Watteau visited London. It was Britain’s opportunity to become a Rococo paradise – until Burlington’s carriages trundled home from Italy with his boxes of classical antiquities and a folder of pen-and-ink drawings by Palladio.

The villa he built at Chiswick in the 1720s epitomised his intellectual pedantry, its elevations an uninspired collage of quotations from Palladio’s drawings and books. Inside the house, however, Kent created ‘the ambience of a French bordello’. With its velvet hangings and frescoes of nymphs was it ‘a bachelor’s pad for riotous purposes’? The rooms are too small for dancing, and the stairs too narrow for the skirts of ladies of the court.

In the 1730s, however, Burlington retired from Court and Kent was free to reveal and showed his true personality in masterpieces such as the state bed at Houghton Hall, a magnificent barge for Prince Frederick, and the Marble Hall at Holkham. At Esher Place in Surrey and at Stowe he created Picturesque gardens inspired by living and breathing the Italian landscape for so many years. It was Kent, wrote Horace Walpole, who leaped the fence and saw that all Nature was a garden.

In his last decade – he died in 1748 – Kent was given the opportunity to realise his vision of a classical Arcadia at Rousham in Oxfordshire. And, to Mowl, it is a sex-mad Arcadia. The statues, temples and fountains are interpreted as symbols of the bisexuality of the client, General Dormer. Is there documentary evidence of the General’s ambivalence? Not a jot. Doubt it, however, and you are in denial: there is ‘not so much a conspiracy as an embarrassment, very English in its nature’ about the true meaning of Rousham. Why? ‘The English have an abiding horror of homosexuality and bisexuality’, as shown by the fate of Edward II and Oscar Wilde. And Kent – with his ‘huge, knowing eyes and trim, pouting lips’ – epitomised a bisexual century.

Mowl’s writing is so engaging, however, that by this stage the reader cares little for historic evidence. It is not so much a biography as a point of view; Kent’s actress mistress and her two children receive a single sentence. I was reminded, above all, of Sacheverell Sitwell’s evocations of the Baroque. Kent is as much a work of stylistic art.

However, what you remember is not so much the sex – although I have never seen the word ‘buttocks’ so many times – but the vitality of Kent’s genius. Kent himself said, ‘the truth is I had as leave make a drawing as write a letter’, and Mowl has a gift for putting his hero’s concepts into prose. And, too, the utter likeability of a man who died of ‘high feeding & life & much inaction’: that is, too much food, too many friends, and too little exercise. A Kent design is never just a design. The client who has commissioned a garden feature receives a drawing for a handsome obelisk – around which a circle of floppy-eared bunnies dance in the moonlight. ‘Someone who could throw off those cheerful seductive sketches must have made the sun shine every morning.’