Harry, grandson of Queen Elizabeth and sixth-in-line to the throne, and Markle, star of U.S. TV drama "Suits" will tie the knot next Saturday at Windsor Castle, home to the British royal family for nearly 1,000 years.
With celebrities expected to join the queen and senior royals for the ceremony and reception, thousands of journalists from across the globe will descend on the picturesque town of Windsor.
"It's absolutely marvellous. It's going to be a very special day for everybody," Harry's father Prince Charles said during a visit to France this week.
Harry, 33, a former army officer and one-time royal wild child, met his bride-to-be on a blind date in July 2016 after being set up through a mutual friend. Markle, 36, said she knew little about her royal date while Harry said he had never heard of Markle or watched her TV series.
"The fact that I fell in love with Meghan so incredibly quickly was confirmation to me that all the stars were aligned, everything was just perfect," Harry said in an interview to mark the engagement last November.
"This beautiful woman just tripped and fell into my life, I fell into her life."
Saturday's wedding will take place at St George's Chapel of Windsor Castle, the queen's home west of London and the oldest and largest inhabited fortress in the world.
Some 40 monarchs have called the castle home and the chapel contains the remains of 10 kings, including Henry VIII and George VI, Elizabeth's father.
Set against all this tradition, Markle is a stark contrast in modernity. As a divorcee, with a white father and African-American mother, her background has provided a source of huge interest and comment, not all positive.
Harry's Kensington Palace office issued a rebuke to the media in November 2016, decrying the sexism and racism Markle had suffered in some press reports.
However, both her divorced parents, mother Doria Ragland, a clinical therapist, and father Thomas Markle, a former TV lighting director for soaps and sitcoms, will play "important roles" on the day.
Markle is due to arrive at the chapel in a car with her mother, while her father will escort her down the aisle.
This wedding has drawn comparisons with some remarkable episodes of recent royal history: Edward VIII's relationship with American divorcee Wallis Simpson, which led him to abdicate in 1936, and the queen's late sister Margaret's decision to call off her marriage to an equerry Peter Townsend.
"Meghan will bring a new perspective to the royal family," royal biographer Claudia Joseph said. "Obviously she comes from a very different background and ... that's hugely important to take the royal family into the future."
The younger son of the late Princess Diana, Harry has always been a hugely popular figure member of the royal family.
The impact of her death threw the prince off the rails, and his teenage years were overshadowed by negative headlines. In 2002 he admitted smoking cannabis and getting drunk when underage in a pub near the royal family's country estate.
He later scuffled with paparazzi outside a London nightclub and caused outrage by dressing as a Nazi officer at a party.
He began to get his life back on track after joining the army, serving two tours of duty in Afghanistan and escaping the media scrutiny and other trappings of his gilded upbringing.
Now a campaigner on mental health issues, he says he was close to a breakdown in his 20s. Such frank admissions of frailty has resonated with Britons as has his natural ease when mingling with the public.
"All that has served to do is make him even more popular."
A poll last week found 71 percent of respondents had a favourable view of Harry. That made him the second-highest rated members of the royals, just behind his brother but ahead of the 92-year-old queen.
Markle, who was born in Los Angeles, made her first TV appearance in a 2002 episode of the medical drama "General Hospital" and has appeared in other TV shows and films.
In 2011, she married film producer Trevor Engelson but they divorced two years later. She achieved greatest fame as an actress for her starring part as Rachel Zane in the legal drama "Suits". She bowed out of the series last month, after her character married her long-time love interest.
Meghan will not become a princess in her own right, but her unlikely marriage to Harry has led many to describing it as a magical children's story.
"The Americans love the British royal family and when you have an American actress marrying a British royal prince, it is the stuff of fairy tales," biographer Joseph said.
However, certainly not everyone in Britain agrees and an opinion poll this week suggested more than half the country would not watch the wedding.
"The idea that someone's aspiration should be to marry into someone else's wealth and status, the idea that Meghan Markle wasn't already successful in her own right, I don't think that's ok," Graham Smith, the chief executive of the anti-monarchist campaign group Republic, told Reuters.
"That's not my idea of a fairy tale."
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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