Since the lockdowns, gardening has not been considered eccentric. It has returned to the centre of life, not just for the over-50s. During most of the Easter break and on bank holiday, I was kneeling in flower beds without being considered odd. I was not even praying.

I have been rethinking eccentricity while reading Todd Longstaffe-Gowan’s new book, English Garden Eccentrics (Yale; Paul Mellon Centre). He did not include me on my knees. Instead he selected 21 gardens, many of which were grand creations of the 19th century. As most of them are unfamiliar, his detailed presentations enlarge the range of conventional histories of English gardens. They need his historical skill because almost all of them have now vanished. In an endnote he sets out their former locations, a valuable resource for keen garden hunters.

One of the few fortunate survivors is Friar Park near Henley, where Sir Frank Crisp commissioned a huge rock garden from the 1890s onwards, which became known as the Henley Matterhorn. As Longstaffe-Gowan notes, it was bought in the 1970s by George Harrison, the Beatle, but he forebears to add that his widow, Olivia Harrison, takes a keen interest in its planting and especially in its huge rock garden. She has introduced excellent blue Himalayan poppies and white woodland trilliums, among much else, and helps them to flourish.

At this point, I wonder about “eccentricity”: is a personal Matterhorn with meconopsis eccentric? Privately, I long for one. Longstaffe-Gowan explains that he regards eccentricity as a state apart, “somewhere between madness and dull normality”. It depends, surely, where you locate the centre.

Longstaffe-Gowan rightly accepts that people he classes as eccentric were not necessarily defined as such during their lifetime. Indeed many were not, least of all Sir Francis Dashwood, whom he includes nonetheless because of his 18th-century grounds at West Wycombe. They include the very caves in which members of the notorious Hellfire Club used to party with naked women, without fear of a fixed penalty notice.

Were those garden parties eccentric? Deep down I bet some of you are wishing you could have attended. The gardens can still be visited as they are maintained, without naked women, by the National Trust.

West Wycombe’s gardens include a temple and a parlour of Venus, installed at the time of Dashwood’s marriage to a rich widow: Horace Walpole described her as a “Presbyterian prude”. Did she blush, then, when these two garden features were rounded off by a swelling mound with a long passage underneath, evoking parts of the female body?

John Wilkes, Dashwood’s political contemporary, remarked that the entrance to the underground parlour was “to shadow out to us the entrance by which we all come into the world”. Above it was a statue of Mercury, a symbol, Longstaffe-Gowan suggests, to “guide the souls of men to paradise”. I disagree: it was surely a witty allusion to mercury’s role as the treatment for venereal diseases, at large in Venus’s sphere.

Was this horto-porn eccentric? It was racy, surely, and in questionable taste. The Hellfire caves were also constructed to give work at a time of high local unemployment and a spectacular rise in food prices after bad harvests. Will Boris Johnson embark on a basement excavation under Downing Street if economic life becomes really tough in the next 18 months? Dashwood was witty and daring and a bit much, but I do not consider him eccentric.

To clarify eccentricity, Longstaffe-Gowan cites the psychoanalyst Donald Winnicott, famous for his life’s work with children. Winnicott distinguished “creative apperception” from “compliance” and praised the former as what “makes the individual feel that life is worth living”.

Compliance, for Winnicott, does not mean complying with rules you yourself have made. It means “the world and its details being recognised but only as something to be fitted in with or demanding adaptation”, presumably of oneself. Compliance “carries with it a sense of futility for the individual” and the idea that life is not worth living. Dashwood and his friends had a creative outlook on the world and continued to enjoy it.

So did many whom Longstaffe-Gowan looks back on as eccentrics. Quite a few of them commissioned caves and tunnels, none more so than William, fifth Duke of Portland, who built underground passages beneath the bleak mansion his family had acquired in London’s Cavendish Square. He also built passages beneath and beyond his country seat, Welbeck in Nottinghamshire. They are wide enough for two carriages to pass each other without colliding.

The Duke was indeed a curious fellow, who kept his lower trousers tied up with string and carried an umbrella in all weathers, but his tunnels were not a way-out originality. They were extreme developments of the fashion for building tunnels for tradesmen so that they would approach a grand house without intruding on its view.

I cannot agree with the theory, cited approvingly by Longstaffe-Gowan, that the Duke was a model for Badger in Wind in the Willows. Their houses indeed have tunnels and they agree on the principle that “there’s no security, or peace and tranquillity, except underground”. In gardens I know the natural habits of badgers only too well: they tunnel without any Duke inspiring them.

Longstaffe-Gowan’s eccentrics like to have hermitages and hermits in their big gardens. In the 1760s Sir Rowland Hill at Hawkstone in Shropshire had a huge grotto and a Hermit’s Lodge with a model of a hermit that moved its lips automatically and answered questions in a hoarse voice. Like all “eccentricities”, the grotto should be seen in context: it is a descendant of the poet Pope’s famous prototype in Twickenham about 30 years earlier. Hermitages were fashionable in grand gardens like Painshill in Surrey, though a toy hermit was a novelty.

In Cheshire, until reading Longstaffe-Gowan, I had no idea of the remarkable Victorian garden that Eliza Broughton contrived at Hoole House in the 1820s. She was estranged from her husband and among her bedding plants and other features had a “Sea of Ice”, made of grey rock, to evoke alpine scenery near Chamonix. Again she is an extreme example of a fashion, the one for alpine gardening.

I also enjoyed reading about William Stukeley, who moved from London to Grantham in 1726 and wrote about his fear of the supposed “pure nature’’ of country life. New migrants into the country may agree but he soon found that his “ancient country complexion” had returned to his cheeks. He then assembled a collection of curios which travelled from house to house with him. His dominant idea was that Druids had held the doctrine of the Trinity and were the native British forerunners of Christianity. This mindset may seem eccentric but, again, it was not unique.

Eccentricity lies in the eye of the beholder, not the agent. Edith Sitwell, as Longstaffe-Gowan reminds us, remarked that she was not eccentric: she was just more alive than other people, like an electric eel in a pond of catfish. I will settle for that. I will continue to encourage gardeners to throw off sparks while pursuing what they love in life.

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