On 9 November 1951 at Kirtling, Newmarket, Lady Mary married Peter Whitley (22 October 1923 Singapore-25 January 2003) of Leighland House, Roadwater, Watchet, Somerset, a son of Sir Norman Henry Pownall Whitley KCB, MC.
After their marriage, the couple was given the Lord Cambridge's London townhouse in St. James's Square.