Gardening: Scene by the limner of Bath: In the first of an occasional series on gardens in paintings, Anna Pavord looks at Thomas Robins's 18th-century study of Painswick in Gloucestershire

'AND HERE'S another one of the garden, a bit later on in the year.' In sitting-rooms, lecture theatres and village halls all over the country, audiences slump exhausted under an avalanche of garden images. Click, another herbaceous border. Snap, another wonky tree, cut off just at the point at which it had become interesting. Flash, a monumental pink thumb blanks out the foreground. 'Such a pity. That was one of my best shots. Hellebores, you know. Not the easiest plants to photograph. Greenish flowers, greenish leaves. But, my dear, the form, the texture. Such a pity.'

We take the instant image for granted now. We can capture any scene we want: new house; new baby; gardens before, after and during. That can be a minefield, unless the pictures are well labelled. 'The garden looks gorgeous,' you say, poring over a photograph of old viburnums grown into strange shapes, bulging hedges behind. 'Oh that,' says the owner dismissively, 'that was before we had it done.' What can you find to say, then, about the wall-to-wall paving with which the viburnums have been replaced?

Television works even faster. In programmes such as Gay Search's BBC 2 series, Front Gardens, one minute you are looking at an unreconstructed Thirties semi and then, magically inlaid on the old site, you get the John Brookes refit. Instant gratification.

Just as we reach for a camera, the proud owner of a new garden in the 18th century reached for his limner. In 1748, Benjamin Hyett, a Gloucestershire squire, used Thomas Robins, described on his gravestone as 'limner of Bath', to record his newly revamped house and garden at Painswick.

The house sits in the centre of the watercolour, its stables to the right. The main part of the garden lies on a sloping hill on the far side of a small but steep valley, the slope carved into a series of long vistas, each ending with a fanciful garden building. Harebells, pimpernels and lilies of the valley twine among the shells of the elaborate painted border.

The painting is done on vellum and is one of a series that Robins made for Hyett, showing his town house in Gloucester, the views from the garden at Painswick, close-ups of some of the garden buildings: all light-hearted, fanciful, sunny pictures - an Eden without the snake - painted in the same rococo style, which provide almost the only record of the layouts of fashionable gardens of this type.

Self-consciously wiggly paths (as in the top right-hand corner of the painting), fretwork fences and capricious garden buildings were all hallmarks of the rococo style. Hyett was evidently going to out-rococo his neighbours or die in the attempt, and Robins was there to capture the achievement.

You can see why Robins was so much in demand by landowners who wanted records of this kind. He was hot on detail. He tilted the landscape to give the sort of bird's-eye view which meant that nothing had to be left out. On this score, photographs are less accommodating.

Every tree in the new plantations, the line of every path, the position of the flowerbeds, the shape of a pavilion roof, the horses frisking in the pasture in front of the house - Robins got it all in. This makes his paintings extraordinarily valuable as research documents, especially if you happen to be the present owner of the garden in question.

Lord Dickinson is Hyett's great-great-great-great something-or-other but, when he took over Painswick in 1955, the garden on the other side of the valley that Robins had painted so painstakingly had long since been swallowed up in scrub.

There was no way through to the Gothic pavilion at the end of the long beech walk. The plunge pool and the rustic grotto built around the spring that supplied it were buried under ash and elder saplings. Being a forestry man (and unaware that he owned the last rococo garden in the country capable of being restored to its former glory), Lord Dickinson filled the valley with a conifer plantation.

Twenty years later, he was uprooting it because of an item in the newsletter of the Garden History Society. This made the connection between the Robins paintings (which hung in rather an out- of-the-way corner of the house at Painswick) and the garden buildings, which still existed in the undergrowth of the sloping land on the other side of the valley.

Lord Dickinson, urged on by his wife and various garden historians, took the expensive decision (pounds 50,000 was spent in the first year alone) to restore the gardens as far as possible to the state in which Robins had shown them.

With the help of a grant from English Heritage, the Dickinsons have been able to repair some of the extraordinary garden buildings, a Gothic pavilion, the theatrical three-door gazebo shown at the end of the vista on the extreme right-hand side of the picture and, within the last two years, the Eagle House, which appears in Robins's painting behind the stables. It is the one with pinnacles and pointed windows.

The long vista shown as a slight diagonal on the right-hand side of the painting has been recreated with 440 young yew trees. The 'wilderness' either side gobbled up more than 1,000 shrubs: Prunus cerasifera, Viburnum opulus, Rhus typhina and various dogwoods. No plants have been used that would not have been available to Hyett in the 18th century.

The pond has been dredged and the old bowling green levelled. Below the wilderness is a new orchard planted with 56 different kinds of old fruit tree. The tunnel arbour has been rebuilt over the path that runs along the south side of the pond. The latest refinement is the dramatic exedra, the curved, white-painted structure which stands in front of the trees on the top right-hand side of Robins's painting. This has recently been reinstated in that same position.

The original, say the experts, was probably made entirely from wood. The replacement has a steel frame for strength, with wood cladding and lath and plaster covering the larger expanses of the design.

The hanging woods, which set off the building so well in the original painting, fortunately still exist. The Dickinsons have replanted the hedges which Robins shows enclosing the rectangle in front of the exedra. Hornbeam, a British native, was their choice.

Robins died in 1770, aged 54. Too little of his work, most of it watercolour on vellum, survives. His earliest known work was in oil on canvas, a bird's-eye view of Charlton Park at Charlton Kings near Cheltenham, where he was born. The garden he shows has disappeared long since.

His painting of Marybone Park, Hyett's town house in Gloucester, shows a pagoda, the first known record of a pagoda in an English garden. How did it arrive in Gloucestershire? Did Robins perhaps design gardens and garden buildings as well as paint them? The man usually credited with bringing chinoiserie to the English garden scene is William Bateman, whose garden at Old Windsor in Berkshire was also recorded by Robins.

Was Hyett using Robins as his arbiter of taste? And what had suddenly happened in Hyett's own life to enable him to afford this extravagant redesign of the Painswick acres? Perhaps his wife pushed him into it.

Robins's Painswick paintings are not on public view but you can visit the garden, which has one of the most breathtaking spreads of snowdrops in England. They are uncommonly early this year and the Dickinsons, who do not normally open the garden until February, have, for the first time, started their season this month. The garden is open daily (11am-5pm) until 14 February for the snowdrops. Thereafter, opening times are Wednesday-Sunday (11am-5pm). Admission is pounds 2.40.

(Photograph omitted)