The couple, whose romance was known only to their immediate circle, are now taking their honeymoon in Scotland. The quiet ceremony last Friday was the first at the reclusive aristocrat's family seat, Hagley Hall, near Birmingham, since it was granted a licence to hold weddings.
Only handful of guests were present, including the bride's parents, Dan and Gwen, of Bromsgrove, Worcestershire. They were unavailable for comment yesterday.
It is believed the romance blossomed after Miss Clayton's catering firm, Westcote Ventures, won a contract to provide corporate hospitality at the stately home several months ago.
A spokesman for Hagley Hall said Viscount Cobham, 54, and Miss Clayton, 38, will live there on a permanent basis.
Peter Harding, Miss Clayton's former business partner, who helped organise her round-the world voyage, said he had no idea the couple were getting married.
"I had heard rumours about a relationship between the two of them but Lisa is a very private person and there are some things you don't ask about. Although I had no idea she was getting married until after the ceremony, I have to say it was no great surprise."
Viscount Cobham, who lists cricket and shooting as his principle interests in Who's Who, was granted a divorce two years ago on the grounds of his 43-year-old wife's adultery.
She left him nearly three years ago for Mr Mellor, chairman of the Government's new Football Task Force. They now live together at his luxury home near Tower Bridge in London.
At the time of the divorce, Viscount Cobham was said to be deeply upset and claimed he had no knowledge of his wife's affair until Mr Mellor made a statement. The Conservative MP had already split up with his own wife after an affair with the actress Antonia de Sancha.
Viscount Cobham had been married for 20 years but had no children.
Miss Clayton entered the record books after becoming the first woman to sail non-stop around the world in her yacht The Spirit of Birmingham in 1995.
During the 31,000-mile voyage, which took 286 days, she battled with mountainous waves, gale-force winds and twice capsized her boat. On the second occasion, she sent a message back to Birmingham asking the people of the city to pray for her.
But she survived and returned to face allegations of cheating. She was asked to provide the World Sailing Record Speed Council with all her written logs for ratification. No action was taken and the record stood.
Since then she has been awarded a Doctorate of Science from Birmingham University, appeared on This is Your Life and two weeks ago was given the Freedom of the City of Birmingham.
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