"It was all very tongue in cheek but it got the ball rolling. Amal found it funny, but she still made him wait a few days before replying.
"It was George's forward banter which ultimately got them talking.
"Once she replied that was it - it's been non-stop ever since."
Since then, the couple are thought to have enjoyed a whirlwind romance, which led to Clooney proposing with a £450,000 (NZ$880,682) diamond ring last month.
The couple celebrated their forthcoming nuptials with a star-studded party at Rande Gerber's restaurant, Cafe Habana, in Malibu over the weekend.
Understandably, seeing as she's married to Gerber, they let supermodel Cindy Crawford join in the festivities. Yet onlookers were no doubt baffled by the attendance of the world's worthiest musician Bono, who looks about as much fun as a bag of spanners.
Meanwhile, it has been reported that Clooney is on the hunt for a property in London.
The former E.R. doctor is apparently eying up a "posh townhouse" near Richmond to be closer to the lawyer's Doughty Street Chambers in the capital.
"She works mainly in London so he will be moving to the UK on a more permanent basis," the source added.
- Independent