On first glance the list of prestigious brands reads like the wedding gift registry of a wealthy eccentric.

Moët & Chandon is one of eight acceptable champagnes for the ice bucket on the (Steinway) piano. The fashion stakes are high, too, with the posh trenchcoat purveyor , the Savile Row tailor Gieves & Hawkes, and Lamont Sporrans for when only Highland dress will do.

But on closer inspection a more practical bent emerges: Crystal Light Chandeliers to “solve all your chandelier worries”, Asbestos Removals and Event-A-Loo. Then the list starts to make sense – these are the hundreds of suppliers required to keep a castle or two running smoothly.

However, the list of near 750 companies who hold royal warrants granted by either the late or King Charles when he was Prince of Wales is undergoing a shake-up. A warrant becomes void after the death of the grantor, an event that sets in train a massive review that requires companies to reapply so they can continue boasting they provide their goods or services “by appointment to” a senior royal.

A year on from King Charles’s coronation – and despite the recent health setbacks in the royal family, including – this extensive undertaking, which is managed by the Royal Warrant Holders Association, is well under way

King Charles is said to be “looking through” applications from the 172 holders of warrants he granted when he was Prince of Wales who wish to obtain one from him as king now. The decisions on these are expected by the end of this month.

Then the focus moves on to the 578 holders of warrants issued by the late queen, which range from the high-end grocer Fortnum & Mason to the late Queen Mother’s favourite tipple, Dubonnet. Application packs for a warrant from the king have already been issued, with answers due in the autumn.

For companies eager to get in on the act and – for the first time gain the patronage of – completely new applications for warrants from the king and queen (who is becoming a grantor) are supposed to open this month. However, the awards will not be made until 2025.

The history of the royal warrant can be traced back to medieval times, when competition for regal favour was intense. The process was formalised by the 15th century but it wasn’t until the 19th century it took off as a means to promote British business around the world. Queen Victoria granted 2,000 warrants during her 63-year reign.

Craig Beaumont, the chief of external affairs at the Federation of Small Businesses, said companies had told the trade body they were “proud to display the royal arms” and it was an asset to those selling overseas.

The Essex jam maker Wilkin & Sons, which is behind the Tiptree brand, has applied for a warrant from the king in the hope of keeping a long tradition alive. It received its first warrant from in 1911 and subsequent monarchs have continued the tradition.

Scott Goodfellow, the company’s joint managing director, said that a royal warrant “has, for us, always been the best indicator of quality and service and this is recognised by customers both at home and across the globe”.

Warrants are only granted to individuals or companies that provide paid-for goods or services to the royal household for at least five years. They are allowed to use the appropriate royal arms on everything from their packaging and advertising to their premises and vehicles. A warrant is usually granted for up to five years and reviewed in the year before expiry.

It is hard to gauge how much of sales fillip a royal stamp of approval is, with previous analysis suggesting it could be worth up to 5% of turnover. For British companies selling overseas there is particular excitement about the bankability of younger royals, with Prince William issuing his warrant from next year.

Chris Jones, the managing director of Corgi Hosiery in Carmarthenshire, Wales – which makes luxury socks for humans rather than the late queen’s – hopes to hear back soon as to whether King Charles will turn the award he granted as Prince of Wales into a king’s warrant.

“The warrant is very important to our business, especially in export markets like China and Japan,” Jones said. “It is seen as a mark of top quality and is something we have on our socks that nobody else has.

“When we are meeting new retailers it is something that gives them confidence that we make a quality product, and stores like carrying products that carry the warrant.”

However, the royal seal comes with strings attached, one of which is discretion. Roughly 20 to 40 warrants are cancelled each year, with a similar number of new ones granted. Benson & Hedges, for example, had its royal warrant revoked in 1999 with the official reason “a lack of demand in royal households”.

More recently, the lingerie retailer Rigby & Peller lost its warrant in 2018, supposedly because the company’s director June Kenton revealed details of her work with the royals in her book .

If that is the case, warrant holders should tread carefully as the book is light on royal underwear intrigue. The biggest revelation to emerge from her first bra fitting with the late queen was the sovereign’s concern that it might rain and that she was due to host a garden party. (Although Kenton did also reveal giving posters to Diana, Princess of Wales for her sons to put up in their rooms at Eton.)

The warrant review triggered by the queen’s death is said to have caused nervousness in some quarters, with fashion brands in particular said to be concerned they would not be able to satisfy the king of their environmental credentials. There has always been a sustainability requirement but applicants report having to set out what their business is doing to work towards net zero.

“It’s good the warrants are being reassessed,” one applicant said. “Some big UK brands no longer manufacture here, so I expect they will lose their warrants, which is right. It should only be for proper UK companies.”