The thing you probably didn't realise was missing from Kate Middleton's banquet dress

Everyone is talking about Kate Middleton after the Spanish State Banquet — the young royal turned heads in a stunning blush pink Marchesca gown at the Buckingham Palace event.

But if you look closely, there was something else that set the Duchess of Cambridge apart from the other royals: she wasn't wearing a sash.

The Queen, the Duke of Edinburgh, Prince Charles, the Duchess of Cornwall, Prince William and Princess Anne were all seen sporting a sash of some variety.

She, however, was the only one not and now people are asking why.

It turns out, these sashes are called “orders” and are a type of gift bestowed by the Queen to relatives as a thanks for their service to the family.

Many of the Queen’s cousins, children, in-laws and other women who have married into the royal family have them, including royal wives Camilla Duchess of Cornwall and Sophie Countess of Wessex.

The come in variety of orders available, which vary in colour and width.

Royal wives are typically gifted the Royal Victorian Order or the Royal Family Order of Queen Elizabeth II.

But people can collect others as time goes on and they have done more work for the family. Prince Charles himself possesses seven different orders.

While the orders aren’t worn often, they are donned for formal occasions, such as the banquet.

So why has Kate has not been given an order? The most likely reason is time, People reports. The duchess has only been part of the royal family for six years and, being married to the Queen's grandson Prince William, is further removed from her than both Camilla or Sophie.

But it may be down to her work. People suggests while the young royal is often out and about with royal engagements, her tally falls short in comparison to other royals.

In 2016, Kate took on 140 engagements, while Camilla did 221 and Prince Charles 530. Of course, this largely due to having two young children to look after.

However, there is no set logic to the orders. They are left to the Queen to give out at her discretion.

Since she married Prince William in 2011, many have speculated on when Kate will receive an order, likely to be a Royal Family Order of Queen Elizabeth II.

However, this is not to suggest the Queen is not fond of Kate. The two are believed to get on very well. In fact, the British monarch loaned Kate her diamond-and-ruby necklace for the banquet — quite the consolation prize.