LONDON: Britain's royal family will be braced for renewed criticism from Prince Harry and his wife Meghan on Thursday when a Netflix documentary series about the couple airs.

Trailers suggest the Duke and Duchess of Sussex, who stepped down from royal duties and moved to California two years ago, will deliver more embarrassing barbs against Harry's father King Charles and elder brother Prince William.

The first three of six episodes will be released on Thursday.

In March last year, the couple's interview with U.S. talk show host Oprah Winfrey, in which they made accusations of racism and ill-treatment in the royal household, plunged the monarchy into its biggest crisis for decades.

"When the stakes are this high, doesn't it make more sense to hear the story from us?" Meghan, 41, says in one clip released in advance by Netflix.

"No one knows the full truth," Harry, 38, says in a trailer. "We know the full truth." In another clip he refers to people working for the royal household briefing journalists about family members, calling it "a dirty game".

Neither Buckingham Palace nor William's office Kensington Palace are commenting before the release, which comes a week after a racism row involving William's 83-year-old godmother which saw her step down from her honorary role as a royal aide.

Speculation about the documentary has dominated British newspapers for a week, with the bulk of the coverage overwhelmingly negative about the couple, accusing them of making millions from their royal status while attacking their family.

'ACT OF WAR'

"The trailer is an act of war," the Sun newspaper said in an editorial. "This pair aren't only willing to bite the hand that fed them - they revel in it, seeking every opportunity to damage Harry's once-beloved father, brother and sister-in-law."

The Daily Mail was equally scathing.

"The documentary is clearly going to be a grotesque parody. It may be their truth but it certainly isn't one recognised by millions in this country," its editorial said.

When Harry and Meghan married in a star-studded event watched by millions around the world in 2018, they were hailed as the future of the monarchy, bringing a multi-cultural, modern dynamic to the historic institution.

Within two years, amid rifts with royal aides as well as with Harry's brother William and his wife Kate, they quit their royal roles and moved to California to start new lives.

Harry said they did so to protect their mental health and escape the sort of intense media intrusion that his mother Princess Diana had suffered. She was killed in a 1997 car crash in Paris as her limousine sped away from chasing paparazzi photographers.

"I was terrified. I didn't want history to repeat itself," Harry says in one of the Netflix trailers.

Since quitting their royal roles, the Sussexes have gone on the attack against the press. They have cut ties with Britain's four biggest tabloids and successfully sued a number of publications, with further legal action pending.

Ultimately, how the documentary is seen will come down to the viewers. Polls indicate the majority of older people in Britain strongly dislike the couple, while younger Britons are much more sympathetic. Commuters in London suggested the family's woes would be better sorted out behind closed doors.

"When they got married, I was so thrilled, I felt like it was a new era and now I'm just so embarrassed," said book publisher Leah Thaxton, 48. "I just wish those two brothers would be friends again."

Brazilian student Thassea Carratto, 26, said she was looking forward to the documentary.

"Maybe they will reveal many things and it (will) be shocking," she said. "I guess everybody wants to know the secrets hiding (behind) the royal family."