Penkill's importance dates back to the 1850s, when the estate was inherited by the young Spencer Boyd, the last male descendant of an ancient Ayrshire family. With romantic enthusiasm, he decided to abandon his 18th-century house in nearby Girvanand rebuild the ruined medieval castle of his ancestors. By 1858 he and his devoted younger sister, Alice, were able to move into Penkill. Both had strong artistic interests and the castle was soon filled with Spencer's carvings and Alice's paintings, old woodwork and rich tapestries.
The following year Alice met the man who was to determine her future and the history of Penkill. In search of a good painting teacher, she was introduced to the Scottish artist William Bell Scott. The unhappily married Scott and the beautiful, affectionate Alice rapidly fell deeply in love. Their relationship was to be lifelong, and was not only tolerated but also respected by Scott's wife, Alice's family and their friends, who included some of the most famous British literati and artists of the time.
Best remembered today for his ambitious paintings of local history at Wallington Hall, Northumberland, Scott was both a talented artist and a much admired writer on art. Yet it was his poetry rather than his paintings that in 1847 attracted the close friendship of Dante Gabriel Rossetti, who introduced Scott to Pre-Raphaelite circles.
Rossetti's letters give a witty, vivid picture of everyday life at Penkill, where Scott and Alice Boyd spent their summers, painting and writing. He supplied many of the furnishings still in the castle, the blue-and-white china, antique carvings and pieces of old tapestry for instance, and helped to arrange large embroidered wall-hangings made by Morris & Co. Here they were visited by friends such as Christina Rossetti, who filled bowls with fish she had caught with her hairnet; William Morris; Holman Hunt, whose Eastern kettle still stands beside the fireplace; and Lawrence Alma-Tadema, who came to learn etching from Scott.
These visits are recorded by Scott's inclusion of portraits of his friends in the most remarkable work of art at the castle, a huge mural covering the wall of the great circular staircase. Illustrating the medieval Scottish poem The King's Quair, it was begun in 1865, the year of Spencer Boyd's death, largely to provide an excuse for Scott's long visits. Filled with lively figures, including Scott himself and Alice's pet duck, Quasi, its rich colours are still unfaded.
Scott did not stop there, but covered the walls and ceilings of virtually every room with decorative paintings, so that birds and beasts, dragons and sunflowers peer out from every corner. He also designed an extension to the castle, in the form of a great hall, for the picture collection, and laid out what he called an 'old-fashioned garden' for which he designed ironwork that was almost Art Nouveau. Its layout is intact, a rare survivor of an aesthetic-movement garden.
Following Alice Boyd's death in 1897, seven years after Scott's, Penkill remained untouched for 75 years, as though under a spell. Its inhabitants were Eleanor and Evelyn Courtney- Boyd, descendants of Alice's half- brother. Then, in the Seventies, during the dotage of Evelyn, Penkill leapt into the national headlines with the revelation that unscrupulous dealers and neighbours had been persuading her to sell cheaply or give away many of her treasures. The scandal became public when the local milkman fell down dead after trying to wrench from the wall Scott's beautiful double portrait of Spencer and Alice Boyd, which the artist had inscribed 'Move not this picture, let it be for love of those in effigy'.
As a result of these events, in 1978 Miss Courtney-Boyd was forced to sell Penkill and it seemed certain that its interiors would be broken up. Fortunately, Elton A Eckstrand, a Detroit lawyer and a passionate admirer of Pre- Raphaelite art and philosophy, bought the castle complete with its contents. He has repaired the ravages of the Seventies - which included replacing lead stripped from the roof by the milkman - and has bought back several items, such as Christina Rossetti's bed, removed during those years. The castle has been preserved with as few changes as possible, so that today its richly furnished interiors make it hard to believe that disaster was so narrowly averted.
Dr Eckstrand now feels that he is no longer young enough to maintain alone a building of Penkill's importance and has placed the castle on the market. The surprisingly modest price of pounds 1m includes the building, its contents, and nine acres of land. However, the chances of finding another private individual equally devoted to the maintenance of Penkill's fragile interiors seems remote, and so far prospective purchasers have been chiefly attracted by its proximity to the golf courses of Turnberry. It is increasingly likely that Dr Eckstrand will have to remove the contents when the castle is sold.
In 1978 the future of Penkill was considered by the National Trust for Scotland, which concluded that the loss of paintings by major artists - some of which are now in the National Gallery of Scotland in Edinburgh - meant that the castle was not suitable for acquisition by the trust. It would be deplorable if such a blinkered view were to prevail again. In the last 15 years appreciation and understanding of authentic interiors has increased vastly.
Everyone concerned with historic houses now regards the preservation of a complete decorative ensemble as more important than the salvaging of 'treasures'. Penkill's decoration, furniture and textiles are just as important as its pictures. They demand the sort of conservation - and, in the case of the staircase paintings, restoration - that private owners cannot be expected to provide. There is also a strong argument for regular public access to a house of such remarkable interest.
For the trust to buy Penkill would probably not be difficult; but raising an endowment for its maintenance would be, and the trust has no shortage of poorly endowed houses. Yet it is essential that the effort be made.
Despite its Pre-Raphaelite label, Penkill is wholly a Scottish creation. Its existence is little short of a miracle, for nothing comparable survives elsewhere in Britain. Both Kelmscot and Wightwick Manor, England's most famous Pre-Raphaelite domestic shrines, were largely assembled in this century.
When much fuss is being made about the fates of Pitchford Hall, Shropshire, and Brympton d'Evercy, Somerset, two historic houses currently on the market, Penkill Castle's uniqueness needs to be stressed. It is an authentic and powerfully atmospheric relic of its age and is saturated with memories of some of the country's most celebrated artists and writers. Let us hope that if no saviour appears, the National Trust for Scotland will have the guts and imagination to come to the rescue, for the loss of Penkill would be a national disgrace.
The author is the Applied Arts Editor of 'Country Life'.