Britain's Queen Elizabeth II, arrives for the Easter Mattins Service at St. George's Chapel, Windsor Castle. Picture: AP

London - The ritual is as unchanging as it is poignant. For nearly 60 years, after the death of every one of Queen Elizabeth's corgis, a quiet corner somewhere on a royal estate is made ready to receive the mortal remains of the devoted companion.

Such an intimate and private moment is entrusted to one of the Queen’s most senior servants, usually the head gardener. The Queen herself likes to oversee the burial, but there are rarely any other onlookers.

Then, within a few weeks a headstone will appear, marking the life of this much-loved pet. It will be this way for Willow, the last of the surviving corgis bred by the Queen herself and who died on Sunday.

The Mail revealed that the Queen had been hit especially hard by the death of the dog that had to be put to sleep at Windsor after suffering from cancer and other related illnesses. For the Queen is not just mourning Willow, but also the end of an era and of a royal dynasty that began in her childhood.

Like all 30 of the corgis she has owned - and other royal pets including gundogs, labradors and cocker spaniels - Willow’s time as part of the Queen’s menagerie will be recorded in the traditional manner.

READ: Queen Elizabeth devastated over dog's death

It has been like this since 1959 when the death of Susan, the Queen’s first corgi, given to her as a puppy on her 18th birthday by her father King George VI, was marked with a headstone.

On it are engraved the dog’s dates of birth and death along with the moving epitaph: "For almost 15 years the faithful companion of the Queen."

The same words appear on the gravestones of two of Susan’s descendants, Sugar and Heather. And, because Willow is the last of the line, the 14th generation traced back to Susan, the elegy is likely to be just as heartfelt.

There is only one unwritten rule - wherever possible, the animals are buried where they died, which means the final resting place of generations of the Royal Family’s pets can be found at Windsor, Balmoral and Sandringham.

These pet cemeteries have one thing in common: they are all in a secluded and peaceful spot with special resonance for the Queen.

Willow is believed to have been interred close to Frogmore House, the royal retreat in Windsor Great Park where Prince Harry and Meghan Markle will celebrate their wedding with a party on May 19.

Other corgis have been buried closer to Windsor Castle, but Frogmore is where the Queen likes to walk, often with her dogs, far from any public access.