The Duke and Duchess of Rutland: it's one wing for him and one wing for her And who is behind all this? Who travels the world promoting Belvoir as if she has known it from birth? Who has bothered to master every historical fact and family anecdote? Who gets up at 4am during the school holidays to deal with estate business? Who handles the vast rental portfolio? Emma Rutland, 50, was not to the castle born, but she is an intelligent hands-on duchess with several minor careers behind her (she trained at the Guildhall School of Music and Drama and then worked variously as a land agent, tour guide, interior designer) and she has learnt how to make her husband's ailing estate pay. No wonder they managed to reach "a state of equilibrium" where they have separate quarters under the same two-and-a-half acre roof and the castle wins hands down. Too much was at stake for it to be any other way. They say they will both live in the castle for the sake of their children. "In the hope of reducing some of the disruption to their lives." But equally, they must find it expedient to live in the castle for the sake of the castle. Their solution is medieval in its utter pragmatism. When David became the 11th Earl in 1999, his family seat in Leicestershire was a chilly, inefficient edifice sliding into ruin, with death duties of £9 million and far too many staff. Emma's practical approach was well illustrated by a disastrous night soon after they moved in. The children woke her to report that water was cascading into the two libraries. She pulled her Barbour on over her nightdress, yanked on her wellies and went on to the roof to investigate. A dead pigeon was blocking the drain. I slid down the lead roof on my bottom and dug it out with my bare hands. That dead pigeon taught me a lot. She installed birds of prey which have since become a tourist attraction. "We [modern duchesses] are not spoiled creatures sitting up in a tower having our nails filed," she told me in the summer. At Belvoir, Emma Rutland went on to discover skills she never knew she had on a canvas bigger than she'd ever imagined. Her stylish mark is everywhere. She made over as if she were personally inventing the stately make-over. She created order out of chaos. The control and the results excited her. "I always say I am the chief executive here," she said. I love my job. I run it all. David's the chairman. He's involved in other things, but not the nuts and bolts. We have a great relationship, whereby he totally trusts me and my judgment and I take things to him for the rubber stamp. After the interview, I went back to her to check I had got that bit right. It made him sound like a cipher. Was it true to say her husband was a shy man, uneasy in social situations, as I'd heard, and preferred his field sports and archival interests to running the estate? She wrote back to say he was "very involved in everything." Later the same week, I received an extravagant new book, written by the duchess, called Shooting: A Season of Discovery, with a picture of her on the front cover, gun in hand, wearing a fur hat and fur-trimmed suede gilet. Belvoir Castle was a dreamy blur in the background. What struck me on reading the book was how much time she had spent on other grand estates - in one season, she had visited 20 different shoots all over Britain - as well as running her own and promoting Belvoir abroad. The union of a sparky farmer's daughter from Powys ("I didn't know an Honourable. Let alone a Lord") and the stolid heir to a castle that had been in the family for 500 years was viewed with cynicism by some of their friends. Had I understood what joining this family entailed? More importantly, could I breed? When a mutual friend introduced them at a party, David Granby (as he then was) remarked: "I like the cut of her jib." The card he handed her at the end of the evening read: "Marquis of Granby, Registered firearms dealer." In her naivety, she thought he might own a pub. The marriage turned into a business partnership of pure gold. The heir to the dukedom had not only found a woman who bore him the necessary two sons and three dazzling daughters, but helped to turn his fortunes around as estate manager, hostess, marketing supremo and interior designer. She, in turn, acquired a showcase for her entrepreneurial talent, a country life she loved and the chance to wear glorious frocks. Perhaps because she herself is in a new relationship ("with a man who works on the estate""), the duchess is keen to record that her husband "strayed" first. "In August 1999, just weeks after the birth of our son, Charles, I learnt that David was having an affair with a lady in London," she says. I can remember even now how the pain cut through my heart, leaving me wretched, angry and bitter. They underwent counselling and renewed their vows at Charles's christening. But their teamwork in repairing the estate had merely disguised the disrepair of the marriage. A crucial and precious ingredient had gone: trust. By 2009, when she threw a party for her husband's 50th birthday, the duchess suspected he had a new mistress ("The lady in question had been living on the estate for a number of years.""). She tried to be philosophical: "Affairs happen and part of me hoped that this one would fizzle out." She says it was her elder children who persuaded her than she should not "accept the affair and endorse it as normal" and who helped them reach the two-lives-one-castle compromise. So she and the children will stay in the converted Nursery Wing that serves as their "intimate" family home away from the public areas, and he will live in the Shepherds" Tower, where they had intended to move as a family. It allows the couple to "work together to preserve the heritage of Belvoir and remind visitors that, as far as the castle is concerned, it's very much business as usual." Exactly. Far from being difficult to fathom, it is a situation that is surprisingly easy to grasp. Read Elizabeth Grice's interview with the Duchess of Rutland at www.telegraph.co.uk/lifestyle/9403109/Emma-Rutland-of-Belvoir-Castle-A-thoroughly-modern-duchess.html