The "first class" creation is made from more than 3,000 postage stamps - each of which features the head of his subject's grandmother.
Mr Mason, a 66-year-old retired art teacher from Hednesford, Staffordshire, has previously created stunning images of the Queen, Barack Obama, Nelson Mandela and Simon Cowell among many others.
The new 3ft by 4ft picture took two weeks to create, with the talented former teacher, of Greenheath Road, spending at least six hours a day working on the artwork. His works are created from thousands of used postage stamps, with the largest pieces using up to 20,000.
"I'd see myself as more of a royalist than a Cromwellian I suppose, and of course I'm angling for a knighthood as well," joked the grandfather-of-two.
The picture is due to go on display in The Art Gallery in Tetbury, Gloucestershire, just a few hundred yards from Prince Charles's famous Highgrove residence.