Queen Camilla and Catherine, Princess of Wales are likely to receive "heirloom" jewellery from their husbands for Christmas

Speaking to Slots Temple (https://www.slotstemple.com/), Grant said: "They exchange light-hearted, joke gifts on Christmas Eve.

"But on Christmas Day they give more meaningful presents. These can include heirloom pieces - jewellery passed down from the late Queen, the Queen Mother, or Princess Diana to the King or Prince William, and then on to Camilla or Catherine.

"There's still a large amount of personal jewellery in the family that hasn't been publicly seen, so passing on heirlooms is very likely."

However, the royal wives may also receive "contemporary" new pieces too.

Grant added: "They also give new jewellery. The royals do buy from modern jewellers - for example, Catherine has been seen in pieces made by a close family friend.

"So Christmas gifts could easily include both antiques and contemporary designs."

Camilla is unlikely to receive a ring from Charles, because she has so many, or a tiara, because the headpieces are typically shared between the women in the family.

Grant said: "Camilla favours pearl necklaces, classic earrings, and brooches - much like the late Queen. Those are the most likely gifts.

"Rings are possible but she already has many, so they're less likely.

"Tiaras are extremely unlikely because the Royal Collection already holds a large number that they all share and rotate."

Although it is a possibility William could gift Catherine something for their new family home, Grant insisted they would probably prefer to choose such items together.

Of William's gift choices, he said: "Almost certainly jewellery - earrings, necklaces, bangles, or a small brooch.

"They might also give something for the home, especially since William and Kate have recently moved, but larger items are usually chosen together.

"Realistically, a piece of jewellery is the most likely Christmas gift."