And as Prince Charles and the Duchess of Cornwall were welcomed by M&S boss Sir Stewart Rose, the retail mogul couldn't let the presence of two distinguished guests pass by without comment.
'We're particularly honoured you've both joined us today. It's what we know in retail speak as a 'twofor' - two for the price of one," he joked, before adding to great laughter from those present: "I could have made it a 'bogof', (buy one get one free) but I may find I may pay for that eventually."
Camilla is believed to be a big fan of the store, and apparently gets her shopping from the chain's Marble Arch branch. And she demonstrated her loyalty by wearing a dress and jacket from M&S' popular Per Una ladies' range for the occasion.
She was offered a glass of a South African wine to sample during the visit, promoting her spouse to joke: "Have you got a glass already? I knew it wouldn’t take you long!", before the pair went on to browse some of the goods on offer.
After the royal couple paused to examine a proffered melon, dad-of-two Charles checked out a very practical multi-pack of socks while the duchess perused through the lingerie department.