To the manor born. Then the National Trust took over

Chastleton House had been in the family of Sarah Jewell since it was built in 1610. Then, in 1991, unable to afford

its upkeep, her grandmother sold it off to the National Trust. Last week she returned for the first time to her childhood playground as a member of the public.

When I was a child I always wanted to have a party in the Long Gallery of Chastleton House in Oxfordshire. It is the most beautiful room I have ever seen, with the longest barrel-vaulted ceiling in England, and I wanted to show it off to my friends and to dance up and down on the creaking floorboards as my ancestors had done.

I never did have a party in the Long Gallery but I got married in the 12th-century church next to the house and had a magnificent wedding reception at Chastleton. A huge log fire roared in the Great Hall and the whole room hummed with excitement as we danced and laughed under the beady eyes of my forebears, whose portraits line the walls.

I was the last direct descendant of Walter Jones - the wealthy wool merchant who built the house in 1610 - to get married at Chastleton. Two years after my wedding, in 1991, the house was sold to the National Trust by my grandmother, Barbara Clutton-Brock. The Trust has spent the last six years restoring and renovating the house and it has just been reopened. Last week I returned for the first time to see what changes have been made.

As I drove into the new National Trust car park I felt choked with unexpected emotion. Throughout my childhood my parents had always driven me and my sisters straight up to the imposing wrought iron gates of the house, and we watched with excitement as my grandfather, Alan Clutton-Brock, shuffled down the drive, puffing on his pipe, to unlock them and let us in. Now I was a member of the public, like everyone else, with no preferential treatment.

I walked from the car park through the dovecote field towards the house and was shocked to see a Union Jack flying from one of the turrets. That was something my grandparents would certainly never have approved of. They lived unostentatiously in bohemian disorder in their imposing Jacobean country manor. But the National Trust staff and volunteers were extremely welcoming and the first thing that struck me on entering the Great Hall was how clean it looked. Gone were the cobwebs and the thick layers of dust and the piles of books and envelopes that seemed to cover every surface.

My grandfather, who inherited Chastleton in 1955, was an artist and Slade professor of fine art at Cambridge and was more concerned with his painting or reading than keeping the house tidy. Added to this he had very little money. Looking after Chastleton and paying for its upkeep imposed a crippling financial burden which no generation since the time of Walter Jones had been able to cope with. That is why the house is such a Jacobean treasure; nobody ever had enough money to alter its structure or contents. Sixteenth century Flemish tapestries and 17th-century "flamestitch" hangings still adorn the walls in the bedrooms, and huge 18th-century pewter plates line the walls of the kitchen.

When I was a child it was always exciting to explore the house. My sisters and I used to love running around searching for the secret room where Arthur Jones, the grandson of Walter Jones, hid after the Battle of Worcester in 1651. Arthur was a Royalist and had been fighting for Charles II but the troops were defeated by Cromwell and Arthur galloped back to Chastleton with Cromwell's soldiers in hot pursuit. His quick-witted wife, Sarah - my childhood heroine - hid him in the secret closet over the porch and although the pursuing soldiers found his exhausted horse in the stables they couldn't find him.

Sarah saved Arthur's life by lacing the soldiers' beer with laudanum and saddling up one of their horses for his escape as the soldiers slumbered. My sisters and I used to lie on the bed in the secret room and pretend we could hear the horses galloping towards us. The bed has now gone and the entrance to the room is barred with one of the National Trust's trademarks: a rope. It's a small restriction, but to me it was the most powerful symbol of the change of ownership.

Most of the access to the house is completely unrestricted, however, and visitors are free to wander around wherever they want. The Trust has restored the house with great care and sensitivity and it has very successfully maintained the atmosphere of gentle decay, yet many of the visitors I spoke to said that the wooden furniture needed a really good polish, not just to make it shine but to preserve it. One man told me he felt so depressed by the general state of dusty disrepair that he was going home "to have a stiff drink". To me, of course, the rooms all seemed cleaner than I had ever seen them. But they also felt emptier, despite the people milling around.

I felt sad that the house is just a showcase now without any of the family there and without the hope of any more family celebrations to make it sing. Mine was the last of many happy weddings at the house. Dorothy Whitmore-Jones, who lived at Chastleton until 1857 and who brought up her seven children there, wrote in a letter to a friend about the marriage of her daughter Frances: "I invited the neighbourhood to a dance which really was a very gay and pretty thing; all those blue and pink gossamer- looking girls moving about in this beautiful well lit hall was well worth seeing and so thought our guests, who expressed a wish that there might be an annual marriage at Chastleton."

Although the visitor can wander at will, the rooms are guarded by National Trust volunteers. Their presence, although very friendly and benign, still felt like an intrusion to me. They were a constant reminder that my fantasy of one day inheriting Chastleton was never going to happen. The only guardians of the house in my grandmother's time were her cats; she had 20 of them and they would hiss and arch their backs at any unwelcome intruders. Both my grandparents used to show people around the house at weekends but my grandfather's opinion of visitors was entirely pragmatic. He would look out of the lead-latticed window of the oak parlour after lunch and when he saw a car or a coach approaching he would rub his hands together and say with a wry smile, "Oh good, here comes another bottle of gin up the drive."

Chastleton House can by visited by pre-arranged appointment only (telephone: 01608 674284) but it is fully booked until March 1988.