The rules Meghan and Kate have to follow when wearing a tiara

The Duchess of Cambridge and Duchess of Sussex have to adhere to many royal protocols – from the requirement of neutral hosiery to muted nail polish.

And there are two important rules both Kate Middleton and Meghan Markle have to follow when wearing one of the palace’s crown jewels; a tiara.

Etiquette expert Grant Harrold, who is also known as The Royal Butler, told us that diamond tiaras can only be worn after 6pm for evening events, and are typically reserved for married women.

Before marrying into the royal family, we never saw Kate or Meghan wearing a tiara in public.

“For married ladies, it was a sign of status and would show you were taken and not looking for a husband,” Grant explained.

“For the gentleman, it was a clear sign not to make advances toward the lady in question.”

The Duchess of Cambridge wore the Cartier Halo tiara on her wedding day in April 2011, while the Duchess of Sussex donned Queen Mary’s diamond bandeau headpiece when she wed Prince Harry in May earlier this year.

Those were the only exceptions to the 6pm rule, and at all other times we’ve seen Kate in a tiara have been after dark for formal occasions such as official state dinners and balls.

We’re yet to see Meghan don one for a second time.

When it comes to royal rules around jewellery in general, there are a few that are actually just urban myths.

It’s widely believed that the royals do not wear diamonds in the daytime, but Grant has told us that this simply isn’t true.

In fact, he revealed “the more significant event, the more likely you are to see them wearing diamonds – specifically when there is a reason.”

While Kate is unlikely to wear pieces such as the Queen’s dazzling Nizam of Hyderabad necklace to a daytime engagement, diamond earrings and delicate bracelets are not off-limits.

The Queen and Kate also regularly wear bejewelled brooches, particularly on overseas visits or royal tours.

The Duchess of Cambridge has sported the diamond encrusted Maple Leaf brooch, which originally belonged to the Queen Mother, on both her royal tours of Canada in 2011 and 2016, as a tribute to the host nation.

Grant added that jewellery would be chosen to reflect the tone of the event and naturally, statement pieces would be kept for evening engagements.

He said: “Kate and Meghan often wear diamond earrings and both their engagement rings, of course, contain precious stones.”

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