How Lady T's selfish son destroyed our marriage

'Seeking closure': Diane Thatcher
13 April 2012

I am really a private person, and to be doing something like this goes deeply against my grain. I wouldn't be doing it unless it served a greater purpose.

I want closure with Mark Thatcher and to show him that Christian humility does not include being his personal doormat; that's why, after 20 years, I have decided to tell our story.

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• On the eve of our wedding Mark threw a pencil at me

Mark and I were introduced by a mutual friend at a party in Dallas on October 1, 1984. It was three days before my 24th birthday. I knew that he was Margaret Thatcher's son and that he was in town - it had been in the papers that he had been dating Karen Fortson, an heiress from an old-money Texan oil family.

I was immediately struck by his boyish charm - he had the kind of endearing smile, twinkle in the eye and charisma that pulls you in. He had a great sense of humour, too, and he made me laugh. It didn't hurt that he was good-looking and dressed immaculately.

We talked about how much I admired Mrs Thatcher and I recall that our first conversation was largely about her, which I found endearing. He doted on her and that was important. I figured that anyone who loved his mother that much must have been raised well. He was fascinating, different from any man I'd ever dated before.

Connoisseur

After chatting for a while, I realised it was getting late and said I had to leave. He kindly offered to give me a lift home, which I graciously declined since I'd arrived in my own car.

[She drove one of her father's Corvettes, he had a white Lotus with red racing stripes and an exhaust pipe that he'd had customised to emit sonic booms].

Within a couple days of our meeting, he'd managed to get my phone number from a friend and he called to invite me to dinner. I remember not being too surprised that he'd followed up, as I'd felt a chemistry between us. I was very excited about seeing him again.

That first date was enchanting. We went to a restaurant and he showed he had great taste - he was very much a wine connoisseur. When he walked me back to the door of my apartment he kissed me on the cheek and I thought that showed respect. He didn't ask to come in. He was a gentleman.

Gracious woman

That led to many other dates at the nicest restaurants but, since he travelled out of town often, I continued to see other men. I didn't see the point of sitting at home waiting for him. I was young and determined to have a good time, and the Eighties Dallas social scene was most obliging.

After a few months of dating, Mark voiced his disapproval about my seeing other men. I laughed it off, referring to them as "insurance" so I had company when he was away.

When we were dating, he was charm personified. He'd bring me boxes of chocolates and he regularly sent ginormous floral arrangements to the office at the real estate agency where I worked. He wined and dined me, took me on trips and constantly told me how much he adored me.

People said he wasn't intelligent but he is a very well informed, very bright man and a very quick thinker. It's just that he doesn't always think straight and has a very short attention span. Eventually, other men seemed rather boring when I compared them against Mark. He even started attending church with me.

For Christmas 1984 he took me to London to meet his mother. It was awkward because I knew so much about her and she knew nothing about me and he must have introduced dozens of other girls to her. We stayed at Chequers. I had a four-poster bed and a hot-water bottle. The fashion that year was bright tights and I wore bright fuschia ones.

I remember Mark addressed her as Prime Minister. "Prime Minister," he said, "this is Diane Burgdorf." I didn't have to curtsy to her but it was very formal.

I think Mark had been in awe of his mother since he was a child and he obviously ran the women in his life past his mother to get the prime ministerial approval. If she hadn't approved of me, I think he would have dropped me.

At the time, his mother could make a material difference to his life. His business depended on networking and he wouldn't do anything openly of which she disapproved. He cared deeply what she thought about his personal as well as business affairs.

We shook hands and then we sat down and chatted before going into lunch. Sir Denis was there. He had an excellent sense of humour which made things easier.

Nowadays, Lady T and I have a mutual relationship of respect but for a long time I was sure that she wondered if I had ulterior motives. I was taking her blue-eyed boy away from her. She is a very gracious woman and she was always kind, but it's a visceral feeling you get when you know someone is trying to figure you out. It was the way she would look at me. I felt judged. The fact was that even if she had been a nobody, I would still have fallen in love with Mark.

Usually at lunches with her we wouldn't be the only guests. There would be a group of people and the conversation inevitably would lead to politics. Lady T would hold forth. I take my right to vote seriously, I try to stay up on politics, but it's not my passion. I would listen.

Engagement ring

When we were in the room alone, she would change the conversation to clothes - I think to try to make me feel comfortable. But I'm not a clothes-horse either. She'd ask what label I was wearing and I'd have to say I don't know.

Lady T was a good cook. I remember one time after she left office she did an incredible Sunday lunch with roast beef and Yorkshire pudding for us at her house in Dulwich.

Mark was encouraging about the impression I was making - he would say: "You're doing all right."

After our first visit to Chequers that Christmas, he said: "Now you don't need the insurance" (of dating other men). He said it jokingly but then he added that he didn't like it and wished I'd see just him.

But I was pretty certain that the "insurance" was one thing that kept him interested in me. It made me a conquest. His brain is hard-wired for a good challenge, and I guess I became that to him. His personality is such that, if something comes too easily for him, he loses interest. He craves risk, challenge and reward.

Mark needs always to have a woman in his life for the ego kick. He needs constant adoration because he is basically insecure. When we went out together, even though he was trying to win me, he would be looking at other women in the room. But Dallas teemed with gorgeous women and I asked myself: "What man wouldn't look?"

We did not live together before we were married. It was against my beliefs and if it entered Mark's mind, he never asked me. He knew what kind of girl I was and that is one thing that attracted him to me. He also knew that his mother wouldn't have approved. Lady T definitely is a moral woman, a Christian. She has never approved of Mark's twin Carol living with the Swiss ski instructor Marco Grass.

After about a year-and-a-half, we were at Mark's flat in Dallas and he said: "I think it would be a good idea if we get married." That was his proposal. He never said why he'd fallen in love or what he loved about me.

But I was head-over-heels in love with him and I really believe he was in love with me, whatever his definition of love was. What I didn't realise was that our definitions were completely different.

Mine is fidelity, loyalty and honesty. I didn't always get any of that from him. In fact, I really wonder whether, when he said his wedding vows, he ever intended to keep them. We would end up saying them a second time in 2003, because after his unfaithfulness - two affairs that I knew about - I felt the first time wasn't sincere.

We bought my engagement ring at Asprey in London. It was a marquise cut diamond. He never told me what it cost but it was flawless so I am sure it was a lot. We had a prenuptial agreement though his finances were something he never discussed with me.

Facilitator

[In February 1984, there was a huge controversy over Mark's alleged involvement in a deal promoted by his mother, in which he represented a British firm awarded a £300million contract to build a university in Oman. In 1985 Mark Thatcher was allegedly paid £12million for acting as a middleman on a £20billion arms contract with Saudi Arabia for which his mother lobbied. He has denied the latter allegation.]

The rumours that Mark was an arms dealer plagued him from the beginning of our marriage. If I had believed he was an arms dealer, I wouldn't have married him. As far as I know, he never did anything illegal. I asked him about it in an indirect way before we married.

He said - not in so many words - that he wasn't doing anything to give me cause for concern. He was a facilitator, it was all about whom he knew and who he could introduce to whom, and that was why he was rewarded.

After our wedding, my mom and dad stayed at Chequers with Sir Denis and Lady T. They were political conservatives and they had a high regard for her.

Mark had bought our house in Dallas before we were married and it was put in his name. I was so busy with my latest job at a bank that I was happy to just let him make the decisions about our home.

Etiquette

He worked with the decorator. He designed the swimming pool. He chose fabric wallpaper for the walls. He hung a painting of his mother, copied from a photograph, over the fireplace in his library.

It's been taken down now and is with Mark's collection of things waiting to be shipped to him when our divorce is final, but I liked it at the time because her hair matched the mahogany panelling.

[They also had a house in Eaton Terrace in exclusive Belgravia in London. According to Thatcher's biographers, Mark bought it for £800,000 in 1989 with funds from an offshore company with ties to one of the alleged middlemen in the 1985 Saudi arms deal and sold it two years later for £1.3million, claiming it was "too pokey".]

For the first two years I really enjoyed being Mrs Mark Thatcher. I couldn't wait to get our stationery printed up with my married name.

Southern women still observe the etiquette. Did that make Mark think I was naive? Maybe. Little did he know. Another Texan, Jerry Hall, used to say: "Underneath the blonde hair there is a very smart brunette."

I'd quit my job at the bank so I'd be free to accompany Mark on his overseas business trips. I travelled with him right up until the time our first child, Michael, was born on February 28, 1989, in Dallas.

Ballistic

Mark and I lived very well. He loved nice clothes - he had loads of tailored suits and dozens of pairs of bespoke shoes and he expected me to dress beautifully. But I never had to pay a bill. He took care of everything.

In hindsight, maybe the idea was that as long as my bills were paid, I'd never ask where the money was coming from. Some of it I am sure was from his investments.

I knew about Ameristar and Emergency Networks [American aviation fuel and security companies in which Mark Thatcher had invested] but he never applied to be a permanent resident of the US after we married because he did not want to be taxed by the US on his worldwide income. He would come in on a visitor's visa and leave when the number of days they allowed him were up.

He had offshore accounts in the Channel Islands and did his banking there throughout our marriage. After the first year of our marriage we never filed tax returns together. So I had no idea what he was worth.

Mark could be very secretive. I knew he was a mover and shaker and a wheeler-dealer but he just wouldn't tell me anything. Whether that was because he didn't trust me or because he wanted to protect me, I just don't know.

He never gave me any reason to believe he was corrupt but after the coup attempt in Equatorial Guinea, I realised there were things he could have done that I never found out about.

People crossed our paths who gave me the creeps and I would try to engage him in conversation regarding his business pursuits, not because I was being nosy, but because I was his wife and cared about him. It upset me that he was not more forthcoming. I felt he never really trusted me, maybe because he didn't trust himself.

Mark is extremely competitive. A lot of his identity is tied up in being successful. It's also very important to him to be recognised, to feel important. But underneath the self-confident and arrogant veneer there was a very insecure man.

His mother doted on him. Soon after we married we visited Downing Street and Lady T handwashed all of Mark's shirts, pressed them and folded them neatly in little plastic bags for travelling. Mark used to refer to moments like that as "little spurts of mothering". He would say to me: "Oh, she had a spurt of mothering today."

Mark had a lot of repressed anger. He would go ballistic sometimes over little things. Even moving a couch to a different location could set it off. Sometimes his anger scared me. He would get very impatient when he was driving, regularly cutting people up in traffic.

English butler

In airports, he was like a Sherman tank. He would just plough people down. I'd be in his wake, apologising. He had to be somewhere and everybody else was in his way.

He can be very rude to anybody he thinks is underneath him, or who he deems should be waiting on him. He'd storm into the kitchen at a restaurant and sarcastically ask: "Where are you flying the fish in from?" There was an incident just last week where he asked one of his mother's bodyguards to go and buy him some milk. That's typical.

He could be very kind to me but he could also be hypercritical. He had no tolerance for what he considered "a whine". If I was struggling with bags at an airport, he'd look back at me impatiently. At dinner parties, he would be rude to me in front of other people as though he was trying to show them who was the boss.

He hated my cat because he had not been allowed to have pets when he was growing up. His parents were busy people and he was at boarding school so he just couldn't understand pets.

After I had Michael, Mark was thrilled to become a father because he had a male heir, but fatherhood didn't come naturally to him. Having grown up with nannies, Mark had a favourite expression he'd use about children which was: "Those things come with nannies."

That suited me fine as I still enjoyed travelling and the nanny was a great help. We maintained homes in Dallas and London and even had a flat in Lausanne because we had Swiss residency permits at the time.

We would purchase economy air tickets and the wonderful, profitable airlines would upgrade us to first-class: nanny, baby and the English butler.

Maternal heartstrings

The butler was a Mark thing, totally pretentious. He hung out at the house and served at dinner parties, which we always had catered, but the rest of the time I didn't know what to do with him so I would have him go grocery shopping.

In Dallas Mark drove a Porsche and I drove a Mercedes or a Lexus. In London he had a BMW and I drove a Mercedes station wagon. He was a qualified pilot and he'd lease a helicopter and we might take a trip in it to Chewton Glen, [a five-star country house hotel on the outskirts of the New Forest].

When Michael was five-and-a-half months old, Mark and I booked a trip for ten days to the South of France to stay at the Eden Roc Hotel in Cap Ferrat. I asked if we could bring Michael and the nanny along. He said it would be too great an expense. I was disappointed, but I thought maybe he was being romantic and wanted to enjoy being alone with me.

I did relax and get into holiday mode but Mark was busy networking. He liked to go into Monte Carlo, meeting people, making connections. We'd go to dinners with people who were fabulously wealthy. IÂd sit there, unable to follow the full conversation and watch them exchanging cards.

After the first week, I phoned home and the nanny was exhausted, and in tears, by her round-the-clock childcare duties. She also let me know that Michael had started crawling, which was just too much for my maternal heartstrings to bear. I asked Mark if we could end our trip a couple of days early and return to be with Michael.

Mark's response was if that was what I wanted then I should go ahead without him. He said the room had already been paid for and he was staying. I was hurt, but I made plans to travel home the next day.

Private investigator

I returned to London, where Michael was staying at our house on Eaton Terrace with the nanny, and then took Michael to Dallas, while Mark went to Paris, where he said he had business to do.

Some time later I saw his American Express bill which included charges at The Ritz in Paris and an air ticket he had bought for Sarah Clemence.

She was an English girl to whom I had been introduced in the South of France. I can't prove that Mark was at The Ritz with Sarah but he was definitely not alone. I saw the actual Ritz room charges and there was no way one person could have eaten all those meals and drunk so much.

I hired a private detective in Dallas and he arranged to have Mark followed in London. He and Sarah went to her flat and did not come out until the wee hours of the morning, according to the private detective.

Marriage counselling

I called Mark and told him he had to come home immediately to Dallas where I confronted him with the information and he did not deny it.

I had the private investigator find out how I could contact Sarah and she agreed to meet me at her flat. We were cordial to each other but the purpose of the meeting was that I wanted to let her know it was not just about the two of them, that Mark had a family, a wife and a son.

She was five years younger than me and single. I wanted to appeal to her sense of what was right and I thought I'd gotten through to her. It was a friendly chat. I believe that only someone who is a Christian can be forgiving like I was and sit down with her husbandÂs ex-mistress. My faith gave me the courage.

Back in Dallas, Mark and I were receiving marriage counselling. What struck me was that Mark showed remorse. He didn't deny having an affair. I had too much proof. He said he really did love me and he was sorry he'd hurt me.

Infidelity

He agreed to cut off all contact with Sarah. He said he didn't know why he'd done it. It was everything I needed to hear. Everything was good again. Except I didn't trust him. That's the most horrific thing about infidelity.

I believed I'd caught their relationship early and later I heard that she had married. I thought, "That's great. I'm happy for her."

[Sarah-Jane Clemence subsequently married Lord Francis Russell, who runs a Chelsea-based property consultancy. They no longer live together. Sarah is the sister of Viscountess Rothermere, the wife of Viscount Rothermere, chairman of the Daily Mail and General Trust, which owns The Mail on Sunday.]

After Mark sold Eaton Terrace, there was a period when we stayed at Claridge's with Michael and the nanny and the butler.

At the end of 1991, we leased a house on Walton Street, right by Harrods, while a house Mark purchased on Tregunter Road for £2million was being renovated. [The four-storey house, set amid a large garden with its own orangery, was the most visible symbol yet of his growing fortune. It was in one of the most exclusive sections of London and was owned by an offshore company registered in Jersey which, reportedly, paid all the household bills.]

As usual, Mark got very involved with the decorating, and the furniture was a mix of antiques and repro and lots of custom-made cabinetry. He had swapped the butler for a chaffeur by then, which was much more practical, given London's traffic and parking challenges.

We went on travelling between London and Dallas. Mark couldn't be resident in Britain for tax reasons but he really missed his mother and his family.

There's a passage in Genesis that says you need to leave your mother and father and cleave to your spouse but I don't think Mark ever really left his mum. I felt Mark put her above me.

Her opinion mattered more than mine and he enjoyed her company more than mine. It didn't emanate from her, it came from Mark. She tried to curb it. She lectured him about spending time with his family.

Responsibility

I never called her Mum or Margaret. Originally it was Mrs Thatcher and then Lady T. I call her that to this day and the kids call her Grammy. I have such respect for her that it doesnÂt bother me that she never said: "Call me Margaret, or Mother."

We saw Lady T and Sir Denis over virtually every Christmas holiday. When we were first married they would stay at our house in Dallas but we only had four bedrooms and with her entourage of bodyguards and US Secret Service agents we couldn't accommodate them after we had children.

Lady T loves being a grandmother. When we visited Chequers, she'd get down on her knees and help Michael play with his building blocks, and gave him so much chocolate the nanny would come back exhausted because it made Michael so hyper.

Mark sold the house in Tregunter Road at the end of 1993, the year our daughter Amanda was born. I'd waited to have a second child because I wanted to be sure our marriage was strong. I had struggled with living in London. I adore the sunshine and I missed Dallas.

Shortly after Amanda was born things started to go wrong again. It was almost as if Mark was scared of the responsibility of being a father.

Attractive

In January 1994 Mark decided he had to get fit and went off to a health farm at Ashram, near Los Angeles. While he was there he met Sheila O'Grady, an American air force pilot. I guessed something was up when he returned home. He was taciturn, moody, constantly criticising me.

My intuition was that he was trying to justify his own bad behaviour. And his style of kissing had changed. I was very tuned into Mark's nuances and he definitely was acting differently. I started praying. I said: "God, if you want me to know something, please let me find it out."

I caught him red-handed. He'd made a lousy excuse about having to go to California again on some business. He was in bed asleep and I went into his dressing room and found his air ticket so I knew what flight he was taking and his hotel - it was all on his itinerary from his travel agent.

I took an earlier flight - and was sitting in the hotel lobby in Santa Monica when he walked in with the woman, who was attractive, dark-haired with freckles. He was shaking. He looked as if heÂd seen a ghost.

Megalomaniac

So we had a little confrontation. He tried to introduce us like she was a business associate but I said: "Come on, I'm not stupid." She left.

I told Mark I was going to take the lovely suite he'd booked overlooking the ocean and he could get his own room. Then I cried. In his luggage with his ticket I'd found a sterling silver rose that he obviously was going to give to the woman and, do you know, it was exactly the same as one he had given me.

I had to overcome the urge to take the rose and strike him. We stayed the night in our separate rooms and in the morning I told Mark I really thought this was the end. He acted a bit resigned, like he was not sure he could keep the marriage going.

To do what I'd done to a megalomaniac like Mark in front of a woman he was trying to impress was totally humiliating.

He is so self-absorbed that he puts his wants and needs above everything. The womanising builds his ego. He's very Clintonesque. The admiration puffs him up. I went home that morning distraught.

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