His comprehension was rare - as if he had been in conversation with earlier gods, William Kent or Robert Adam - but it was fitting. His grandfather, Herbert Jackson-Stops, founded the estate agency of that name, and made his reputation through the sales of some very grand houses, notably Stowe House, in Buckinghamshire, and Witley Court, in Worcestershire. Indeed, the lavish Stowe catalogue of 1921, and of book size, is a collector's item. Gervase Jackson-Stops felt that his own zeal to explain houses came from a need to correct such sales, occasioned by a time when there was no public or government interest in the rescuing of endangered country houses.
Educated at Harrow, Jackson-Stops won an exhibition to Christ Church, Oxford ("the House"). He was always amused that his tutor put down on his list as required reading Burke's Peerage. Over his three years there, Jackson-Stops became a familiar figure in the High, with his laughing face and frock coat. For his cheerful disposition and his ability to assimilate chunks of knowledge with ease, his tutor referred him to him as "an ornament to the House". After Oxford, in 1969, he was awarded the Museums Association Studentship at the Victoria and Albert Museum in London, where he worked in virtually all the departments, absorbing every aspect of architecture and the applied arts.
Alongside a happy demeanour went the determination to reach objectives. In 1975, Jackson-Stops was appointed Architectural Adviser to the National Trust, where he had been the Archivist since 1972. His task was to advise on all aspects of historic house presentation and frequently to write the guidebook. As he went from house to house his car would be crammed with wallet files and vast architectural books, often bearing the label "London Library", and the urgency of each quest made speed limits secondary. On reaching his destination, he would leap from the car as if there would never be enough time to accomplish all that was at hand.
He saw the National Trust as endlessly requiring support and he had scant words for its detractors. "What a ridiculous article," he would say of some spiteful critic. "He just doesn't know what he's talking about." The main charge was invariably that the trust had become too bureaucratic and anaesthetised its interiors. Jackson-Stops realised that, because of the death duty tax, the trust had no alternative but to try and accommodate all houses offered to it. Of course it had to grow, and of course the area representatives had to have their say in the decoration of the houses in their area. Otherwise few representatives would want the job. Also, with his intuitive eye, Jackson-Stops knew he was quite capable of challenging any erroneous artistic decisions of the trust's himself. And this he would do, whilst remaining staunchly loyal to the trust's overall purpose.
Within the National Trust, Jackson-Stops commanded enormous respect. Because of this, he broke fresh ground when single-handed he fought for the rescue of the sadly decaying Northamptonshire manor-house Canons Ashby in the late 1970s. It was the first time that government funds - and not a family endowment - were used to save an historic house. Today it can be seen with all its time-worn beauty restored, a wonderful memorial to Jackson-Stops's persuasiveness and sound historic sensibilities.
He went on to repeat this performance with the much- publicised Calke Abbey, in Derbyshire. In 1984 the Treasury allowed the death tax on Calke to be used to preserve this house in which the Harpur- Crewe family had let the past stand still. So much so that in it Jackson- Stops discovered an early 18th-century bed complete with Chinese hangings that had never been unpacked.
There were not many who could resist Gervase Jackson-Stops's inimitable personal charm. In stature he was not tall and he had an innocent, querying face that seemed never to have left childhood. He had, too, a highly idiosyncratic stammer - which recently he had all but conquered - and to get a stuck word out would click his fingers with increasing rapidity. (Once when in Spain and trying to say "tavola" to the restaurant owner, he could only click his fingers. "Aah," said the restaurateur, thinking he had grasped it, "I know, you want the flamenco - I fix.") This combination of appearance and stammer brought out an immediate sympathy in all but the most hard-hearted of country-house owners.
So passionate was Jackson-Stops's determination to have the achievements of the country house recognised, that he eagerly took on project after project. In the early Eighties, he was appointed curator to the "Treasure Houses of Britain" exhibition by the National Gallery of Art in Washington. For two years, he toured the houses of Britain persuading owners that, if they couldn't lend their Batoni portrait of the ancestor on the Grand Tour or that unique silver christening bowl, the exhibition would not be able to take place. Owners immediately roused themselves to scurry about their houses after him, realising the exhibition's national importance and delighted to learn themselves from his effervescent enthusiasm.
To coincide with the "Treasure Houses" exhibition, Jackson-Stops wrote The English Country House: a grand tour (1985); two more titles quickly followed, The Country House Garden (1987) and The Country House in Perspective (1990). These books demonstrate the clarity with which he could explain the ever-changing patterns of the country-house style.
The success of the Washington exhibition earned him an OBE. He kept the insignia pinned, in throwaway manner, to a classical bronze bust of Diana in his own exquisite folly, the Menagerie. The saving of this eye-catcher in Horton Park, in Northamptonshire, built in the 1750s by the architect Thomas Wright of Durham, was Jackson-Stops's private achievement. When Jackson-Stops heard of it in 1972, he set out in conquest. Trampling across fields and hacking down the undergrowth, he found an architectural dream. He restored one of the finest English Rococo plasterwork rooms, complete with Father Time, the Four Winds, and above the cornice 12 large-scale medallions of the Zodiac. Later he added two further follies in the four and a half acres and, with his friend Ian Kirby, he created a romantic English garden incorporating a formal period design with exuberant modern planting.
The Menagerie was for Jackson-Stops his country house in miniature, and there he gave a succession of parties, often with operas, in the true tradition of the fete-champetre. Only a week before he died he gave his final party to celebrate the opening of his shell grotto with its vivid themes of the underworld. At the Menagerie, with its many reminders of the civilising 18th-century mind, Gervase Jackson-Stops fulfilled his ambitions. There, by his achievements, talk and laughter he brought renewed hope to a more stressed age.
Gervase Frank Ashworth Jackson-Stops, architectural historian: born 26 April 1947; Museums Association Studentship, Victoria and Albert Museum 1969-71; research assistant, National Trust 1972-75, Architectural Adviser 1975-95; OBE 1987; died London 2 July 1995.