LONDON -- Queen Elizabeth II, the second-longest ruling monarch in history, will be celebrated and mourned at a state funeral Monday after her 70-year reign.
And after she made history, it is only fitting that her funeral will make history as well.
The service for Queen Elizabeth II is expected to be the most watched broadcast event of all time.
"It's also a very emotional thing to say goodbye to this person that people didn't only see as the queen, but also as almost like a maternal figure, a mentor to the world," royal etiquette expert Myka Meier said.
Meier says the planning of a royal funeral is carefully charted, and arrangements for the queen's death -- known as Operation London Bridge -- began as far back as the 1960s.
"So even though they knew or they hoped the queen had decades to live, which she did, that's how much planning this kind of event, this funeral, seen as one of the most important ever that's ever happened, has been choreographed," she said.
It is meticulously mapped out, right down to the guest list.
"It's going to be just everybody, from the head of state, head of country, it's going to be the most significant in terms of who is there, globally, in terms of most important people on Earth who want to pay their respects."
And attire is key. King Charles and other working members of the royal family must wear military uniforms. Prince Harry will wear a morning suit.
"When we heard that Prince Harry will be wearing morning attire, we think mourning as in a funeral, but it's actually morning, like the morning versus the night," Meier said. "And that simply means it is a very traditional UK dress, something that is worn during the daytime. It's usually dark colored."
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Women of the royal family, including non-working royals such as Prince Harry's wife, Meghan, must wear a traditional black lace veil in some form.
It will be similar to what Princess Anne wore last year at her father's funeral, and a young Queen Elizabeth wore 70 years ago at the funeral of her father King George VI.
The royals traditionally wear black for mourning after it was popularized by Queen Victoria, who wore black for 40 years after the death of her husband Prince Albert.