When it comes to packing for a trip, we reckon the Duchess of Cambridge is just like the rest of us.
You know, she'll chuck in some smart wear, some casual wear, a toiletry bag, a book or two, maybe even some special underwear...
But there's one garment that she carries with her everywhere she goes that most of us just wouldn't think of packing.
In fact, it's not just Kate who has to carry this particular item of clothing.
The whole royal household do.
No, it's not sunglasses or swimwear — it's a black mourning outfit.
Yes, whenever a member of royalty is on a trip, they always have a handy mourning outfit on hand just in case one of the family dies while they are away.
If, for example, the Queen were to pass, members of the royal family would be expected to wear black to show their respect as part of normal protocol.
For example, when Princess Diana's father, Lord Spencer, passed away in 1992, the family were on a ski trip in the Alps.
However, they all wore black for the return journey to the U.K., having had appropriate outfits packed.
Of course, there have been times when the royal family have not been prepared for a death in the family.
When George VI died in February 1952, the young Queen and Prince Philip, who were on a Kenyan safari, issued a photo ban until they were dressed in their mourning outfits.
So you can see why it is such a good idea to over pack the royals' luggage.
You just never know when you might need a certain garment.
And who cares about how heavy the suitcase is?
It's not like Kate or William will be lugging that big old thing across an airport is it?