Sir Paul McCartney's wedding to Nancy Shevell is "imminent".
The couple flew into the UK from her native New York last week to finalise the details for a small intimate ceremony at the 69-year-old musician's home in Sussex, South East England, with stacks of chairs and boxes of champagne flutes already arriving at the estate.
A source said: "They will be marrying imminently. They are very excited and almost everything is in place. Friends and family have been put on standby."
The couple - who have already selected their wedding rings from famous Los Angeles jewellers Neil Lane - are planning a party in the US for Nancy's loved ones after their British ceremony, which is expected to take place early next month.
The source added to the Daily Mirror newspaper: "Nancy would have liked to get married in New York but she knew an English wedding would make Paul happy.
"In the end they decided to marry in the UK and have a party for all their American friends at their home in the Hamptons later.
"I don't think I've ever seen a couple so besotted with each other."
Paul's wedding to the 51-year-old heiress - who he has been dating since 2007 - will be his third marriage.
His first wife, Linda - with whom he had children Mary, Stella and James and adopted her daughter Heather - died of breast cancer in 1998, 29 years after they tied the knot.
In 2002, he wed former model Heather Mills - with whom he has eight-year-old daughter Beatrice - but they split in 2006, with their divorce finalised two years later.