Details on Paul McCartney's 'Huge' Engagement Ring to Nancy Shevell

Paul McCartney, 68, is set to marry his girlfriend of four years, Nancy Shevell, 51, and on Friday the businesswoman debuted her pricey new engagement ring.

The exclusive pictures obtained by Life & Style, depict Nancy walking in public with a round-cut diamond ring on her finger that reportedly cost Paul over $650,000.

A source told the magazine, "Nancy's ring is huge! You can tell she was excited to finally be showing it off. She was glowing and relaxed and looked like she couldn't be happier. She even gave a thumbs up when asked how her and Paul were doing. Clearly the couple is very happy."

This will be the Paul's third marriage. The singer married his first wife Linda in 1969 and they remained together until she died of cancer in 1998. He wed Heather Mills in 2002, and that relationship ended in a messy divorce in 2008.