Prince Harry and wife Meghan, the Duchess of Sussex, will fulfill their final royal commitment when they appear at the annual Commonwealth Service at Westminster Abbey in London on Monday.

It's the last time they will be seen at work with the entire royal Windsor clan before they fly off into self-imposed exile in North America.

The service marks the end of a two-month drama that began when the couple announced plans to walk away from their roles as senior members of Britain's royal family.

They go into a world where they will have to earn a living, pay their own way and even open some doors for themselves.

Pauline Maclaran, co-author of Royal Fever: The British Monarchy in Consumer Culture, said Harry and Meghan's absence would definitely be felt at Buckingham Palace.

"I think this is a blow because I don't think (the Windsors) would have envisaged that the slimmed-down monarchy would have actually meant that there was no role for Meghan and Harry," she said.

"I mean, they really brought a new dimension to the royal family brand."

Less than two years ago, Harry and Meghan were seen as a golden couple that would help extend the royal family's appeal to a new generation.

Their wedding on May 19, 2018, united a grandson of 93-year-old Queen Elizabeth II with the former Meghan Markle, a bi-racial American actress who had starred for seven years on the US television series Suits.

George Clooney, Serena Williams and Elton John attended their wedding at Windsor Castle, which ended with the royal couple kissing for their flag-waving fans and riding through the streets in a horse-drawn carriage.

But the horses were barely back at the stable before pressures intensified on the couple, who became the Duke and Duchess of Sussex on their wedding day.

Even before the ceremony, Britain's tabloid newspapers featured stories about a rift between Meghan and her father.

When Meghan became pregnant, some commentators criticised her for jetting off to New York for a baby shower, a strange American tradition to many in Britain.

Meghan's supporters saw racism at work. Harry publicly defended his wife and directed his anger at the intrusive media he has resented all his life because of the paparazzi's role in chasing his mother Princess Diana on the night in 1997 when she died in a Paris car accident.

The prince himself was stung by media reports of a split between him and his older brother, Prince William.

The notion that the brothers and their glamorous wives would be a royal "Fab Four" for the 21st century began to fade.

"For me, and for my wife, of course there's a lot of stuff that hurts, especially when the majority of it is untrue," Harry, 35, told ITV News last year.

"I will not be bullied into playing a game that killed my mum."

Australian Associated Press