Here's the one rule Kate Middleton has to follow at Prince Harry and Meghan Markle’s wedding

And it seems a little strict...

Prince Harry and Meghan Markle are set to wed this weekend at St George's Chapel, Windsor Castle - marking an end to months of wedding prep.

Now that we know the full list of the royal bridal party and that Prince Charles will be walking Meghan down the aisle, the focus has shifted to what we can expect from the wedding day fashion-wise.

Will Meghan choose an English or a Canadian designer to create her dress? How will she do her make up? And what colour hat will the Queen opt for?

Kate Middleton has also been a topic of conversation, with people wondering if there are any rules that the new mum will have to stick to for the big day.

Well as it turns out - yes, there is one big rule that the Duchess of Cambridge must abide by on Prince Harry and Meghan’s big day - but it’s not what we expected.

As a royal woman, Kate is expected to always wear a hat for formal occasions - and this royal wedding is no exception.

While we all browse hats and fascinators as part of our wedding shopping prep, it is not an option for the Duchess, but a strict rule that she has to follow.

Good thing Kate looks great in hats!