Credit: Dave M. Benett/Getty; Jackson Lee / Splash News

Paul McCartney spared no expense when the time came to buy an engagement ring for Nancy Shevell, his love of nearly four years.

The former Beatle, 68, proposed to NYC businesswoman Shevell, 51, two weekends ago "during a romantic candlelit dinner for two," a source recently told Us Weekly. As for the ring? It's estimated to be an impressive $650,000!

This will be the third marriage for the legendary rocker. His first wife, Linda, died of cancer at the age of 56 in 1998; married for 30 years, they had three children together. McCartney's second marriage to Heather Mills in 2002 ended with a messy, expensive divorce in 2008.

McCartney and Shevell began dating in the Hamptons in 2007, while he and Mills were already estranged.