Mark Thatcher's ex-wife Diane to marry £15 million American tycoon

She has found new love with tycoon James Beckett, who she started dating quietly soon after the split was formalised.

They were introduced by friends in Diane's home city of Dallas, Texas, where she moved to from South Africa following the breakdown of her 20-year marriage to Baroness Thatcher's son.

Mr Beckett has amassed more than £15million publishing guides for sports memorabilia, which is a massive market in the United States.

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The new couple share a devout Christian faith, with 58-year-old Mr Beckett "finding God" 11 years ago following a heart attack.

Diane, who has custody of her 18-year-old son Michael and daughter Amanda, 14, said:

"I told my friends there was no way I'd ever embark upon a new relationship unless that man was a Christian, and not just in name, but in his heart.

"Jim's integrity and high moral standards are a direct result of his strong faith. I had a deepening awareness that this man was who he really said he was – and that he was worthy of my heart.

"Our friends brought us together, but our mutual love for Christ is the reason we found each other. We'd really only broached the marriage topic for the first time last weekend.

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"Last Sunday I told my children that they shouldn't be surprised if Jim asked me to marry him this year."

Diane, 47, went on: "The thing I'm learning about Jim is that when he firmly makes up his mind about something, he doesn't let grass grow beneath his feet.

"But I was still really surprised when he asked me to marry him a few days after our discussing the topic.

"He dropped to one knee holding a little velvet box with a ring inside and proposed. He told me how much he loved me, why he loved me, and how he was convinced that the Lord had caused our lives to intersect.

"I'd already decided in my heart that should he propose I'd accept, so that part was easy." The couple have yet to fix a date.

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Mr Beckett, who has three daughters from a previous marriage, is one of the world's leading authorities on sports memorabilia cards, which are licensed by American teams and can command five-figure prices at auctions.

The former university statistics professor turned what started as a hobby into a publishing empire, Beckett Media, issuing price guides considered essential by collectors.

He sold the company in 2005 and started a charitable foundation that sets up networking seminars between church and business leaders.

It aims to bring "attention to best business practices consistent with Biblical principles".

He has said he found God at 47, after his coronary, adding: "I define my life as before and after the heart attack. A person in my situation is either going to run to the Saviour or away from him."

Despite his own considerable success, he is known – in sharp contrast to Diane's ex-husband – for what colleagues call his "remarkable lack of ego".

Diane's first marriage was a high-profile event orchestrated by Sir Mark at London's Savoy Chapel in 1987.

But the couple's life together fell apart after they moved to South Africa.

While there, Sir Mark was implicated in a coup bid in Equatorial Guinea and pleaded guilty. He was fined £265,000 and given a four-year suspended sentence.

The conviction means he cannot enter the US and so can see his children only when they travel abroad.

Son Michael is now a star of his high-school American football team and last month helped them reach the state finals with a spectacular diving catch in front of 10,000 spectators.

Diane says she and Mr Beckett plan a "quiet family ceremony". And she has informed her former husband of her engagement. "He seemed surprised but offered me his best wishes," she said.

She has also told her former mother-in-law. "I still have enormous respect for Lady T," said Diane.

Asked if she will take Mr Beckett's name, she said: "Absolutely, yes."