Britain's Prince Harry and Meghan Markle. (Yui Mok/Pool via AP)

Meghan Markle hasn't said if she will wear a tiara at her upcoming royal wedding, but if she does she'll be able to choose from one of the world's most remarkable jewelry collections.

That's because Queen Elizabeth II, the grandmother of her husband-to-be Prince Harry, has hundreds of tiaras squirreled away in locked vaults, and royal tradition holds that the queen will let Markle borrow one of these sparkly heirlooms.

There's no shortage of diamonds in the queen's collection, to say nothing of rubies, sapphires and emeralds. One tiara is designed so that its emeralds can be replaced by pearls — depending on the rest of the outfit, of course.

London jewelers are hoping Markle will bring tiaras back in fashion when she walks down the aisle. (AP Photo/Kirsty Wigglesworth)

The bride's actual choice probably won't be known until May 19 when she walks down the aisle of St. George's Chapel to marry Harry and officially join the royal family. But some of London's most exclusive jewelers are devoutly hoping she won't turn her back on tiaras in favor of a more egalitarian look.

Markle, a 36-year-old American actress, is known for her contemporary fashion sense and could surprise everyone by skipping the tiara in favor of a less stately, more accessible look. But Omar Vaja, sales director at the renowned Bentley & Skinner jewelry shop in London, thinks she will follow tradition.

"Her style of dress is quite modern and casual," said Vaja. "So she'll probably go for something that's small and modest. There's quite a lot to choose from. I think we're talking about hundreds of tiaras."

He says tiaras often have been kept in aristocratic families for generations, passed down to wear on special occasions.

Prince Charles and Lady Diana Spencer are shown on their wedding day. (AP Photo, file)

Vaja and other jewelers in London's tony Mayfair district have a vested interest in seeing Markle carry forward the tiara tradition. He expects this royal wedding — like earlier ones — to spur interest in tiaras and other vintage treasures that his shop is known for.