The mantra “never complain, never explain” was first attributed to Benjamin Disraeli, the 19th century prime minister, although it was Queen Elizabeth II who was known to deploy the maxim to great effect during her 70-year reign.

Next week, the Duke of Sussex will be turning what he has called the family motto on its head when he returns to London for a high-profile trial in the High Court.

Prince Harry is expected to appear in court on Monday for the opening day of his case against Associated Newspapers. Later in the week he is expected to give evidence as part of the long-running case.

It is the latest and, for now at least, the last in a series of legal battles for the prince against the press.

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He will join six other high-profile claimants including Sir Elton John, Baroness Lawrence of Clarendon and Sadie Frost, when he accuses the publishers of the Daily Mail and the Mail on Sunday of illegal information gathering. The publisher has strenuously and repeatedly denied any wrongdoing.

And so the stage is set for Harry’s greatest complaint yet, and a chance to explain his reasons for doing so when he appears in court.

King Charles III, in a kilt, and Queen Camilla, in a blue coat and feathered hat, chat at the Braemar Royal Highland Gathering.

The King and Queen will keep calm and carry on in Edinburgh

CHRIS JACKSON/GETTY IMAGES

Since his school days, the duke has often broken his late grandmother’s rule. In his memoir Spare, Harry recalled an anecdote about being wrongly accused of cheating in an art project when he was at Eton.

He wrote: “It turned out to be nothing at all and I was later cleared by the exam board. But the damage was done. The accusation stuck. Brokenhearted, I wanted to release a statement, hold a press conference, tell the world: I did the work! I didn’t cheat! The Palace wouldn’t let me. In this, as in most things, the Palace stuck fast to the family motto: Never complain, never explain.”

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While he is making his appearance in court, his family will not be present to show their support.

Instead, the King and the Prince of Wales will join other senior members of the royal family in adopting another oft-repeated family edict: keep calm and carry on.

The King is not expected to see his younger son while court proceedings are active and will instead carry out official duties 400 miles away in Scotland.

Prince William and Kate Middleton greeting a crowd in Tobermory on the Isle of Mull.

The Prince and Princess of Wales, known as the Duke and Duchess of Rothesay when in Scotland, will be in Stirling and Falkirk next week

AARON CHOWN/PA

It means that on Monday, Charles will be in the Throne Room at the Palace of Holyroodhouse in Edinburgh where he will be joined by John Swinney, the first minister of Scotland, to host the Scottish Investment Forum. There will be talk of new technology and a chance for Charles to sample some local whisky: a bread-and-butter royal engagement.

The Queen will join the King in Scotland and is expected to have her own engagements.

Meanwhile, the Prince and Princess of Wales will be on joint manoeuvres north of the border with engagements in Stirling and Falkirk, far away from the court action as Harry’s nine-week trial gets under way.

It is understood that there has been no contact between William and his brother for some time. One source suggested that “hell would have to freeze over” before the brothers were able to meet again.

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If that’s the case, William and Kate’s engagement on Tuesday won’t offer any hope of relations thawing any time soon, when the Waleses head out on to an ice rink to meet members of the Team GB and Paralympics GB curling teams preparing for the Winter Olympic and Paralympic Games in northern Italy.

Kate and William will be offered the chance to try their hand at curling, aligning themselves with one of Team GB’s most successful winter sports to date and one that has earned them six Olympic and two Paralympic medals so far.

On Thursday, as Harry’s trial gets under way and begins to hear the testimony of witnesses, William will be in Bristol to meet a finalist from his environmental Earthshot prize and to visit the University of Bristol’s Isambard-AI supercomputer where scientists hope to use its calculating power to help develop new drugs to combat heart disease, Alzheimer’s and cancer.

What William makes of his brother’s battle with the press will be kept to himself.

Certainly, like his brother, William has also been known to complain when he feels it is necessary, notably over his feelings about the BBC over Martin Bashir’s 1995 Panorama interview with his mother, Diana, which was obtained through deception.

Harry’s complaint is ongoing with the outcome set to unfold in the coming weeks.

He will have his day in court and is expected to be seen in court on several days next week, and will also be attending private meetings relating to his charities during his visit to the UK.

The Duke of Sussex leaving the Rolls Buildings in London after giving evidence in the phone hacking trial, surrounded by security and media.

In 2023, Harry gave evidence in the phone hacking trial against Mirror Group Newspapers

AARON CHOWN/PA

Separately, his battle to have his police security reinstated continues as he awaits the findings of a risk management board.

The famous “never complain, never explain” motto is likely to come under strain.

While Elizabeth took the maxim from Disraeli, even he appears to have adapted it from the scholar Benjamin Jowett’s Maxims for a Statesman written between 1873 and 1876.

In it, Jowett lists 11 maxims for “statesmen and others”, which included: “Never quarrel, never explain, never hate, never fret, never fail.”

For the royal family at the moment, the “never quarrel” rule may be a little harder to adopt.