The 37-year-old former actress is seen inspecting her dress and veil, which had the flowers of all the countries in the commonwealth sewn into it.
"53 countries, oh my goodness", she tells an off-camera companion as she views her wedding veil, which featured blooms from 53 Commonwealth territories (as well as one for her home state of California and another for Kensington Palace).
During the documentary, viewers will see footage collated over more than a year which ITV boasts will offer "a unique insight into Her Majesty The Queen's role as a figure on the global stage and the baton she is passing to the younger members of the Royal Family".
It also seems to promise plenty more candid prenuptial Markle moments.
Prince Harry still gets nervous when he bumps into his grandmother in the corridors of Buckingham Palace.More news: Amber weather warning issued as Storm Helene set to hit Mid-Wales
More news: Coca-Cola Is in Talks to Make Marijuana-Infused Drinks
More news: NCDOT warns residents about Florence flooding interstates, highways
The Princess Royal says: "We were kept very busy".
We don't know about you, but we're totally here for Meghan's British accent.
The trailer shows the Duchess of Sussex being reunited with her Givenchy bridal gown for the first time since her wedding day on May 19, as Royal Collection specialists prepare the dress for a new exhibition.
Besides embarking on her first royal tour with Prince Harry in just a few weeks, Markle will also continue Queen Elizabeth's work with the Commonwealth as she accompanies Harry in his own duties as a Commonwealth Youth Ambassador.
The newlyweds are due to arrive in Australia in October, before travelling to New Zealand, Fiji and Tonga.