LADY Henrietta Spencer-Churchill, eldest daughter of the Duke of Marlborough whose family seat is Blenheim, divides her time between Fulham and the Oxfordshire estate. But not for her the windy west wing of the grand palace. Lady Henrietta has a snug farmhouse which was used by Blenheim’s deputy farm manager on her father’s 11,500 acre estate.

She’s been there for eight months, which is a long time for someone who has moved house four times in as many years. She house-hops because just as she begins to settle down in one her father sells it. ‘Basically, I go where I’m told, which is wherever my father wants me to go,’ laughs Lady Henrietta. ‘That’s why I never got around to doing anything much to the other houses. But this one is different. It’s in the middle of the estate and dad will not be selling me off. This time it’s roots – I hope.’ She’s the divorced mother of two boys and militarily organised, which is why, when she was given three weeks to move from her last house into this one – a ‘Georgian one with bits added on’ – she coped.

Lady Henrietta, 36, is a hands-on interior decorator, who does the books, runs the company and counts among her clients society figure Paddy McNally. Her second book on decor is called Classic Decorative Details. She is slim and elegant with pre-Raphaelite hair and wears a Marks and Spencer waistcoat and “what has been described as a car rug” wrap-around wool skirt. She speaks with upper-class plumminess and has two black Labradors by her side like ancestral sentinels.

The house overlooks a valley. It hasn’t been a working farm for years, but retains its outbuildings. ‘The garden has gone mad because I haven’t had the time to attack it, but this spring I’m going to get the contractors in.’ On the opposite side of the valley is the house of her brother, one-time aristocratic junkie James Blandford. ‘James and I have always been very close.’ She visited him often in prison. ‘The Scrubs was grim, but Pentonville was worse. I didn’t feel embarrassed or ashamed about him being there. I just wanted to be supportive.’

She went into group therapy with her brother and the rest of their family. ‘We had to get to the root of the problem. That was probably very beneficial for me, too. You learn to cope with things.’ She is reluctant to talk more. ‘It has sometimes been ghastly and gone on for a very long time. But, hopefully, we are through all that now.’

James and Henrietta were brought up in Lee Place, a 17th century manor. Their parents divorced when she was one year old and they were raised by her father. She didn’t live in Blenheim until she was 12, when the 10th duke, her grandfather, died. ‘We used to serve in the gift shop at Blenheim and hide on the long balcony overlooking the great hall and make ghoulish noises to scare the visitors.’

It was at Blenheim that she designed her first room, when she was a teenager. On being given their stepmother’s permission to choose their own rooms, James settled on a tiny one stuck between two floors, facing north and with porthole windows. Lady Henrietta, whose style is altogether more airy, decided on one overlooking the lawns and decorated it in blues, pinks and creams. It is this gut feeling for colour and space that she eventually capitalised on in her straightforward and single-minded way. She went on to gain one A-level from St Mary’s, Wantage, followed by history of art in Florence and a course at the Inchbald Interior Design School. ‘I would have loved to have studied law and become a barrister. And I’ve always had a desire to become a detective or criminal investigator.’ In 1980 she married German-born banker Nathan “Booby” Gelber. They had two children – David, aged 13, and Maximillian, nine. ‘David is more like me in character. I’m quite introverted. I like people, but they’re not a priority in my life.’

THEY divorced in 1989 after Lady Henrietta became friendly with financier Richard “Groper” Andrew, who had separated from his second wife, Lady Serena – and they were named in each others’ divorce cases. ‘Everybody gets divorced these days. It’s not a big issue,’ she says frostily. Richard ‘is still a good friend. But I see lots of people. I lead a very independent life.’

Nowadays she lives alone. This is reflected in her home. Her decorating style is one of restraint and economy. The sitting room has sea grass, a gilt sofa and a wicker coffee table with coffee-table books. There are two oils of Cherwell and Palm Beach – ‘nothing very special, but sentimental’ – by her grandfather’s cousin, Sir Winston Churchill. She doesn’t keep ‘anything of value’ in her house. On the contrary, she is more likely to have an old armchair from a junk shop in Oxford. She delights in revamping a “good buy” in some exotic velvet. She gives old prints the same treatment, really believing in the value of impressive frames rather than the content. There are family photos, one of her mother Susan (whose family owns W H Smith) on a Bahamas beach in a billowing canary dress, and many of her children. On a table is a leather-bound order of service from her parents’ wedding. The next-door drawing room is currently being decorated. To make the dining hall she tore down a wall and ripped out a lavatory and woodburner. Now it’s painted National Trust green with Zoffany fabric curtains with puff-ball headings and a dining table piled with showcase books. In the corner is a blackamoor statue. ‘He belongs to an uncle, but has been in the family for a long time. They live abroad and I’ve ended up looking after him.’

The decor upstairs is untouched although she has just put in an upstairs bathroom. Her bedroom is lilac, which she’ll change to blue, and has watercolours by her ‘great, great, great-grandfather or one of my ancestors.’

She smiles. ‘I’m proud to be a member of this family. But it doesn’t influence my life. I’m perfectly normal.