When royal family grants a warrant to its favoured supplier of tea or salmon, it's not only an honour for the firm but also a major boost in the global marketplace.
The strength of the Windsor brand lends its weight to some 800 companies who are eligible to feature the royal crest and the words "By Appointment" on their products.
"It's the ultimate mark of quality and regarded as an international stamp of approval," Andrew Leigh, founding chairman of Scottish smoked salmon manufacturer John Ross Jr, told AFP.
"We've held the Royal Warrant for 24 years and in that time it has opened doors across the world and enabled us to grow the business."
The company now exports to 36 countries and the Royal Warrant has helped increase its export market by 30-35 percent, said Leigh, adding that it would "continue to play a major factor as we expand throughout China, Japan and South East Asia."
Royal Warrants are granted to people or companies who regularly supply goods for a minimum of five consecutive years to Queen Elizabeth II, her husband Prince Philip or her son Prince Charles.
Companies with warrants, which range from multi-national companies to small artisan firms, have the right to feature the coat of arms of whichever of the royals has backed them on their packaging -- more than one royal may grant a warrant to any particular company.
Warrants are not a new invention. Tradesmen in the Middle Ages were granted official recognition, while under king Henry VIII, who reigned from 1509 to 1547, a certain Thomas Hewytt was appointed to "Serve the Court with Swannes and Cranes and all kinds of Wildfoule".
But the process was formalised in the 19th century with the issue of warrants, and the Royal Warrant Holders Association was established in 1840.
Today, there are warrants for high-end goods such as Prince Charles's traditional whisky suppliers and the hunting vests worn by the outdoorsy royals. But at the other end of the scale, holders include a supermarket and a toilet paper manufacturer.
Most are British, with the exception of some French champagne makers and South Korean electronics giant Samsung. Small family businesses rub shoulders with global brands like Twinings tea or Schweppes soft drinks.
A rare few have chosen to leave the royal seal of approval off their packaging: the crest disappeared from boxes of After Eight mints, now made by Nestle, in 2009.
"After Eight is a global brand sold in more than 70 countries. In December 2009, Nestle standardised the packaging to ensure relevance and consistency in all countries, resulting in the royal warrant being removed," said a spokesman for the Swiss food giant.
But the queen's thumbs-up is a sought-after honour for most, especially for manufacturers of luxury goods.
Clothing maker Barbour has the rare privilege of holding warrants from Prince Philip (since 1972), the queen (since 1982) and Prince Charles (since 1987).
"The warrants are recognised as a mark of quality around the world from the United States, throughout Europe to Asia," said a spokeswoman for Barbour.
"We are always very proud when we see pictures of members of the Royal family wearing our products."
The enduring global fascination with the British monarchy -- which burnished its image with the birth of Prince George in July, the marriage of his parents Prince William and Kate in 2011, and the queen's diamond jubilee last year -- effectively means firms with warrants get free advertising.
"The Royal Warrant is seen as a marque of quality and is especially valued in the export market. Countries where it seems to have most impact are the Middle East, Far East, US and Commonwealth countries," said Richard Peck, secretary of the Royal Warrant Holders Association.
He dismissed any suggestion that a royal link might be counter-productive at a time when Britain and many other countries are still feeling the pinch of austerity.
"There is a perception that a company granted a Royal Warrant is expensive, but the converse is true. To retain the Royal Warrant companies must consistently demonstrate value for money, a quality product and reliable and flexible service," he said.
