The secret patch Meghan Markle had sewn into her wedding dress

Meghan Markle's wedding dress secretly had a memento important to her and Prince Harry sewn into it.

The secret patch was a piece of fabric from the outfit she wore on her first date with Prince Harry.

In a clip from a soon-to-be-released ITV royal documentary, it's revealed that Markle especially asked to have the patch sewn into her wedding attire.

She apparently wanted to do justice to the bridal tradition of having "something old, something new, something borrowed, something blue" on her big day.

"Somewhere in here, there's a piece of... did you see it? The piece of blue fabric that's stitched inside? It was my 'something blue'. It's fabric from the dress that I wore on our first date," said Markle in a clip obtained by People.

The classic white dress was also embroidered with flowers representing each Commonwealth country, including a kōwhai  as New Zealand’s unofficial national flower.

The ITV documentary, titled Queen of the World, will be the Duchess of Sussex's first official interview as a royal, and will feature members of the royal family speaking about Queen Elizabeth II and the Commonwealth.

It will air just before Prince Harry and Meghan, who met on a blind date in London in June 2016, come to New Zealand in October.

Newshub.