Sir Paul McCartney is on the verge of announcing his engagement to American heiress Nancy Shevell, US media reports claim.

Shevell is understood to be in the process of finalising her divorce from businessman Bruce Blakeman, more than a year after the couple legally split.

In the meantime, Sir Paul is said to be scouting for a new property near Shevell's New York home on Manhattan's Upper East Side.

Although Sir Paul or Shevell have never formally confirmed their relationship, the couple have been almost inseparable since the former Beatle's divorce from second wife Heather Mills was finalised in May.

Most recently, the pair travelled on a road trip together along America's Route 66, posing for pictures with Beatles fans during the holiday.

Shevell is an old friend of Sir Paul and his first wife, Linda McCartney, who died in 1998 following a battle with cancer.

(by Jason Gregory)