AT AYTON Castle, Lady Christine de la Rue, in red jumper and jodhpurs and wearing dusters on her feet, is skating around what appears to be 27 miles of wooden hall floor. A polishing trick she picked up at the Pucci Palace in Florence. The fire is blazing, sandwiches are laid out on the grooms’ table in the hall – where they play ping pong and do Scottish reels – and Highland terriers scamper about.

The mistress of Ayton Castle, Berwickshire, is a colourful character with a past as dramatic as her castle.

She had a three-year love affair with Prince Michael of Kent. At the time, she was married to the late Sir Eric de la Rue, a man 36 years her senior, and the Prince was a bachelor. Christine, 53, talking for the first time about the relationship which ended in 1975, looks worried. Prince Michael is still a friend. And Christine is loath to jump on to the kiss-a-Royal-and-tell bandwagon.

This expert horsewoman and Captain of the Ayton Castle polo team laughs, remembering the Prince’s reaction when first she invited him to stay in Scotland. ‘I don’t like horsy people,’ he complained. ‘Their houses are so dirty.’ Now he rides with her. And her Gothic-revival schloss, where the Prince, Prince Alexander of Yugoslavia and Christopher Lee have stayed, is as spotless as a Zurich hospital.

Christine, a blonde Norwegian, lives with David Liddell-Grainger, the father of two of her children. She has been providing the Borders with society gossip for years, and has just finished writing what promises to be a compelling autobiography.

Her first marriage at the age of 19, to a Greek lawyer, was annulled after two years because of non-consummation.

‘I wasn’t in love with him,’ she says girlishly, with nervous speed. ‘I married to run away from my mother who told me I was ugly and stupid.’ With the approval of her next husband, the elderly Sir Eric, Christine scandalised local puritans by having a publicised affair with David, who was married to Anne, a cousin of the Queen. ‘Eric was spritely and a father figure but he wasn’t interested in sex after our son St George was born.’ She divided her time between the two men in what was seen – erroneously – to be a bizarre love triangle, and after Sir Eric had a mild stroke he moved into the castle with them. When Christine and David’s son David Henry was born, Sir Eric and David were at the christening.

Christine is not the hard-boiled woman oft portrayed. She’s special – delightful, shrewd, forthright and exuberantly energetic. The warmth of the castle reflects her personality.

FOLLOWING the Norman invasion, a formidable fortress was built at Ayton. When it burned down in 1836, James Gillespie Graham built the present turreted red monster which Henry Liddell, David’s grandfather, bought in 1888.

Until David was eight years old – when his father died and his mother shut up the castle – he lived here with 40 servants. It was used during the war as a girls’ school.

In the Fifties, David camped occasionally in the master bedroom, looked after by one Miss Denham. ‘She mended his long johns and cooked for him.’ After his grand marriage, with a reception at Windsor Castle, he took tons of his furniture out of storage (all had been stored easily in the castle drawing room, natch) and returned to live in the castle. David crammed his fine collection of Chippendale furniture and Staffordshire figurines alongside buys from country house sales.

When Christine moved in, the rooms were gloomy and pigeons roosted in the towers. ‘Ayton was mortgaged. No, I mean morgue-ish.’ For 12 years, Christine has been restoring the interior to its original baronial splendour. ‘David’s wife had put up dishcloth curtains.’ She has worked to a tight budget. ‘I’ve used remnant wallpaper and chosen colours to last 100 years. The dining-room round table cloths are made from old bedcovers.’ In 1990 they decided to take paying guests for £120 a night. The castle sleeps 25 comfortably and visitors can shoot and fish. They also open to the public on summer Sundays.

We do a quick tour of the castle, in less than an hour. When David is upstairs and Christine down, she rings him on her portable phone. ‘It caused great problems at the phone shop when I said I needed a model that worked inside six-foot walls.’ They probably receive long-distance bills. We speed through the dining room with its Adamesque wedding cake ceiling, table to seat an army and picture by society portraitist Barbara ‘Basha’ Hamilton. Into the drawing room which had a trampoline in it when David was young, was then turned into a shop selling cashmeres to visiting Americans, and finally decorated in 1985 for a Victor Edelstein charity dress show. Now it has overflowing bowls of hydrangeas, a grand piano and serious curtain poles. Into the library, with books piled high, family photographs and table set for a cosy dinner.

THEN a 10-minute walk to the family wing. ‘For when the revolution comes and 25 other families move in.’ Up to her second, or perhaps third sitting room where currently she’s hanging her ballgowns. ‘That’s a Victor (Edelstein), that’s Catherine (Walker).’ Into David Henry’s room with a bed for their other son Maximillian. ‘Max has his own room as well, but he likes to share.’ Off to Christine’s room with its 18th century Venetian wooden domed bed with silk hangings and cherub. Then along to her partner David’s masculine room with its single bed with two rifles by it and suitcases piled high.