Andy Burnham faces Balmoral test which Kate Middleton sailed through 17 years ago

The UK Prime Minister is set to become the latest person to face the ultimate royal initiation - the famous ‘Balmoral test’.

Labour leader Andy Burnham, 56, who stepped into the role last month, will be invited to stay at Balmoral Castle at the end of summer, along with his wife Marie, The Telegraph reports.

It’s become tradition and is something that every PM before him has done, but don’t be fooled, as rather than a relaxed summer getaway, it’s more like a high-stakes test.

Popularised by the Netflix series, The Crown, the Balmoral test is essentially an informal term for the unspoken evaluation where senior members of the British Royal Family size up high-profile guests.

From romantic partners, such as Kate Middleton and Princess Diana, to Prime Ministers Keir Starmer and Rishi Sunak, it’s an invite that simply can’t be turned down.

After all, spending a weekend with someone is the easiest way to get to know what they’re really like.

The British Royal Family have been spending summers in Balmoral for 170 years (Keystone/Getty Images)

For those who are unfamiliar, Balmoral is the British Royal Family’s large estate house in Aberdeenshire, Scotland.

King Charles III and Queen Camilla visit every year, as do Prince William, Kate Middleton and their three children, Prince George, 13, Princess Charlotte, 11, and Prince Louis, eight.

The stay typically takes place between August and September, and is when they invite their lucky guests.

The humungous estate covers roughly 50,000 acres of forests and farmland, with over 150 outbuildings, as well as, of course, the castle itself.

When it comes to the test, as per Marie Claire, Margaret Thatcher famously failed it, whereas the late Princess Diana is known to have passed with flying colours.

Burnham will have to be on his best behaviour in order to pass with flying colours (Dan Kitwood/Getty Images)

The royals are reportedly watching on to see how well their guests fit in - no pressure!

As well as Diana, another royal who allegedly triumphed during her 2009 ‘Balmoral test’ was Kate Middleton.

In his book, William and Kate: A Royal Love Story, royal author William Anderson said: “As Kate stood on the riverbank angling for salmon, trout and pike, it quickly became clear to one member of the Balmoral staff that she seemed 'perfectly at home here’.

In fact, she did so well that the following year, her parents Carole and Michael Middleton were invited to a shooting weekend.

So, how on Earth do you pass the mysterious test?

The visit usually takes place during August and September (Tim Graham/Getty Images)

Well, as per Woman&Home royal expert and author Omid Scobie told Harper’s Bazaar, if you’ve scored an invite, ‘prepare to brush up on your royal protocol, have a wealth of talking points at the ready, an outfit for EVERY occasion (from hunting to black tie)’.

He added: “And, most importantly, be on your best behavior at all times."

Omid continued, "Social etiquette is a must! If you don’t like the food, eat it anyway. If you don’t like trampling through the Highlands in the wind and rain, tough! Unlike a visit to Buckingham Palace or Windsor Castle, this is the queen’s private residence and a front-row seat within her inner sanctum."

As for how Andy Burnham does, I guess we’ll have to wait and see…