It’s the biggest abdication since King Edward VIII — and once again, it’s all for the love of an American divorcee.

Prince Harry and his Los Angeles-born actress wife, Meghan Markle, on Saturday night were granted their wish to “step back” from royal duties.

They’ll be stepping back alright — way back, and with a deft shove from Her Majesty.

In a cordially worded heave-ho, the Queen announced that while Harry and Meghan “will always be much loved members of my family,” this will not be the gentle, gradual disentangling from Buckingham Palace that the pair hoped for when they dropped their bombshell on Instagram earlier this month.

No, this is a hard Megxit.

Beginning in the spring of 2020, the couple will be allowed the freedom they covet — freedom from the mandatory pinning on of fancy hats and medals for state events, freedom from required royal overseas tours, freedom from the constraint that they live in gilded but gated palaces in the UK.

But this freedom has a high price.

Under the agreement, the couple will be barred from cashing in on their titles, and can no longer call themselves “His Royal Highness” and “Her Royal Highness,” as they’re continuing, for now, to do.

“Their Royal Highnesses,” the pair persisted in calling themselves after the queen’s statement, on their now awkwardly named Web site, Sussexroyal.com.

But come this spring, they’ll be relegated to the royal hoi polloi, forever known as “Harry, Duke of Sussex, and Meghan, Duchess of Sussex.”

They will no longer receive public funds; in fact, they now owe the British public a small fortune.

Under Saturday’s announcement, the couple must repay British taxpayers $3.1 million recently spent to refurbish Frogmore Cottage, their 10-bedroom, 1801 estate on the grounds of Windsor Castle.

And they must pay commercial rent on the home’s upkeep from now on, the Sunday Times of London reported — even if they spend most of their time in Canada, where Meghan is currently living in a rented Vancouver mansion with the couple’s 8-month-old son, Archie.

The cost of their empty cottage-within-a-castle could amount to around $13,000 a month, the Times found.

In short, Harry and Meghan — like Edward VIII and Wallis Simpson before them, in 1936 — have been booted from the palace inner circle and reduced to fending for themselves as debt-saddled, middling royals.

And that’s just fine by the British public. Nearly 80% of Britons want Harry and Meghan cut off from public support if they’re no longer playing the part of royals, according to a Daily Mail poll.

It’s an intricate, protocol-steeped snubbing.

Harry, who takes pride in his 10 years in the Royal Army, including his two stints in Afghanistan, will be stripped of his military appointments.

No longer will he be “Captain General of the Royal Marines, Honorary Air Commandant Royal Air Force Honington and Commodore-in-Chief of Small Ships and Diving.”

The couple will still be “invited” to attend such set-piece galas as the annual, fancy-dress Trooping the Colour military ceremony, the Sunday Times reported.

“They will happily attend royal family events at the invitation of her Majesty,” a royal source told the newspaper.

But Meghan, as a no-longer-royal, will be barred from wearing a tiara at state functions, should she still choose to attend.

The couple will also be on a somewhat short leash, financially.

They’ll continue to receive an undisclosed amount of “private financial support” from Prince Charles — but otherwise, they’ll be on their own.

They’re hardly paupers — in fact, both are millionaires in their own right.

Harry reportedly sits on a $25 million personal fortune, much of it an inheritance from his mother, Diana. Meghan pocketed $40,000 per episode while filming the cable legal drama “Suits,” and is reportedly worth some $5 million.

Still, they’ll likely want to continue living the luxe life.

Meghan is house-hunting in one of Canada’s most exclusive enclaves — and is eyeing a $27 million waterfront property in Vancouver, according to a report in Britain’s The Sun.

The 108-year-old mansion on four levels features six bedrooms and five bathrooms and 20-foot beach-side walls and tall hedges for privacy.

And their options for growing wealth, rather than just spending it, are limited under their agreement with Buckingham Palace.

In addition to being barred from cashing in on their “HRH” titles, they can’t become brand ambassadors for big companies, the Times reported.

Instead, the couple’s commercial deals will likely be in synch with the charities they’re already involved with, at least to start.

They’ll still get some security support, though the terms for that have not been set.

Perhaps worst of all, under the agreement, while they no longer represent the Queen, Harry and Meghan must nonetheless “continue to uphold the values of Her Majesty.”

The watchful eye of grandmom, Her Majesty, will be upon them both figuratively and literally — staring back at the couple every time they spend a Canadian $1 coin or any of the country’s paper currency, all of which still bear the Queen’s image.

But as stringent as her terms may be, Queen Elizabeth expresses what sounds like some genuine concern for the couple, as they, in her words, begin “building a happy and peaceful new life.”

“I recognize the challenges they have experienced as a result of intense scrutiny over the past two years and support their wish for a more independent life,” she wrote in Saturday’s statement.

It’s a nod to the strain the couple has publicly alluded to suffering as they settled into the reality of their real-life fairy tale: Prince and commoner fall in love, and the fantasy of happily-ever-after yields to the reality of a ravening press and an exacting extended family.

“It’s a very real thing to be going through,” as Meghan said in an ITV documentary of her first, and now only, year as a royal.

And so, more than 80 years after Edward renounced his kingship for “the woman I love,” as he famously declared, Meghan and Harry will find a new “happily ever after” at an uneasy distance from the crown.