“I’m a vistas man,” says Roddy Llewellyn as we stroll around his west Oxfordshire garden. Sure enough, as I peer through a small window in the top of a stone model of the local church spire, my eye is led past a timber arch, across a circular lawn, between four majestic yew columns, through a gate and on across another stretch of grass and over a birdbath before finally resting on a small mirror placed on the wall at the far end of the garden.

Stopping at nothing to create an unbroken view, Llewellyn simply ploughed straight through the middle of a large philadelphus with a JCB. Ten years on, the plant still thrives, albeit in two pieces, among a treasure trove of plants in his one-acre garden in a quiet village on the edge of the Cotswolds.

Here Llewellyn, 56, has found a blissfully tranquil spot after spending many years in the spotlight. Known by many for a much-publicised affair with Princess Margaret in the 1970s, Llewellyn’s true claim to fame is his passion for gardening and a talent for garden design. He has lived and worked in the house — a former pub dating back to the 14th century — for the past 10 years, creating beautiful gardens, including show gardens at Chelsea and Hampton Court, and writing an impressive collection of books and articles.

Now also ploughing his considerable energies into co-ordinating and hosting garden lectures, Llewellyn uses what spare time he has to tend to his own garden. Jovial, dapper and good-looking, he is welcoming, chatty and justly proud of his creation, enthusiastically showing me around and waxing lyrical about his favourite plants.

The garden has an unusual horizontal aspect, stretching widthways across the back of the house and continuing parallel to the street. It is a glorious spot, south-facing and with a breathtaking view over much of Oxfordshire. There is, however, a price to be paid for the view. Being relatively high up, the winds can be pretty fierce, sweeping across the low dry-stone wall that divides the garden from a hay field.

Llewellyn prefers to keep it this way: one of his first tasks after moving in was to eradicate a row of leylandii trees planted along the southern boundary. It was a trade-off between retaining a windbreak, which would obscure the view, or chopping it down and putting up with the occasional buffeting in return for the privilege of enjoying an uninterrupted watercolour sky and an ever-changing swathe of Cotswold countryside directly outside his back door. He plumped for the latter and embellished it further, softening the edges of the garden by chucking handfuls of seed over the wall so that spiky Onopordum acanthium and teasels are silhouetted against the scudding clouds. “I rather like the idea of the garden marching out into the countryside,” he says.

Although surrounded by farmland, the garden is subtly but effectively structured; occasionally, though not predictably symmetrical, it is always well balanced. Llewellyn is a designer with a highly developed sense of proportion and line and describes his main vista as the backbone that supports the rest of the garden. With many years of professional experience behind him, he knows how to get the most from each element to create a satisfying whole.

He makes particularly good use of hedges to define the space and separate it into distinct sections, each with a specific atmosphere. A simple circular lawn, which surrounds a stone-edged pond, is enclosed by embracing walls of yew. A mixed hedge of native hazel, blackthorn, spindleberry and guelder rose softens the transition between cultivated garden and wilderness.

A juvenile hedge at one end of the garden consists of alternate contrasting chunks of purple-leaved beech and golden Irish yew, and a curved 2m-high beech hedge, the crisp bronze and burnt umber leaves glowing in the low sunlight, serves to separate the back garden from a large gravelled area at the side of the house.

Llewellyn has cut strategically placed gothic windows into the beech hedge to allow tantalising glimpses through to the other side. On a more practical level, it also performs the rather mundane function of screening the car-parking area so that it is invisible from the garden. Adjacent to, but not encroached upon by the cars, the gravel garden gives Llewellyn the perfect opportunity to grow drought-tolerant plants. Clouds of purple sage and Eryngium giganteum — clearly relishing the arid conditions — are backed by the yellow-green foliage and dangling magenta flowers of Fuchsia magellanica ‘Aurea’. The twisting stems of Euphorbia myrsinites hug the ground at the feet of a large Jasminum officinale ‘Aureum’, which wends its way through a large clump of rosemary.

This is a plantsman’s garden with a particular emphasis on trees and shrubs, including the unpronounceable Paeonia mlokosewitschii, Viburnum plicatum ‘Mariesii’, the golden-flowered Sophora microphylla ‘Sun King’ and a much-loved Exochorda x macrantha ‘The Bride’, all of them dolled up with a wealth of perennials, bulbs and annuals. “I have a passionate love affair with plants, and then it can wear off, but the test of time is if the love remains,” he says.

Llewellyn has a particular penchant for specimen trees cut into circles in the lawn at strategic points around the garden. Sorbus ‘Joseph Rock’, Liriodendron chinense and an unusual Toona sinensis are included in his collection. He recommends positioning decorative trees so they can be viewed principally from the south to the north, rather than against the brightly back-lit southern sky, which can wash out the colours.

Year-round interest is achieved in the structural plants, with flashes of added colour provided, on my visit, by deep purple aconitum, sugar pink nerines and cheerful white cosmos peppering the borders. When it comes to colour, Llewellyn knows what he likes. Purple and golden yellow are a favourite combination, but dirty pinks and mauves get short shrift.

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