When the King and Queen stood in front of the Colosseum on Tuesday, it was the result of months of work by Palace aides, embassy staff, and government officials in both countries.

Posing in front of one of the seven wonders of the world on the eve of their 20th wedding anniversary, the Queen reminded her husband to turn around for the cameras.

Camilla, the PR transformation of the past two decades, knows the importance of a good image better than anyone. The King hasn’t always been a fan of the waiting press pack, but obliged.

Despite his continuing cancer treatment he abides by the Winston Churchill mantra: “Keep buggering on!” Imagine his frustration, then, when his younger son, Prince Harry, arrived in London for a high-profile court case that was guaranteed to dominate the front pages and detract from his moment on the world stage.

It was a tale of two cities and two very different missions. On Tuesday, while his father was flying the flag for Brand Britain in Rome, a smart-suited Harry was in London, waving to the cameras before taking a pew near his legal team in Court 73. He wasn’t required to give evidence, but had nevertheless decided to travel more than 5,000 miles from his home in California for what was widely billed as “a last throw of the dice”.

It has been a long journey for the litigious duke in more ways than one. When I broke the story three years ago that Harry was suing the government to have his police protection reinstated in the UK, he would have had no idea that it would be such a drawn-out affair.

Harry initially applied for a judicial review to challenge the Home Office’s decision to remove his police security when he quit royal duties. He believed that the royal and VIP executive committee (Ravec) “got the law wrong” and that the threat to his life remained the same. But Harry “comprehensively lost” that battle last February when Mr Justice Lane ruled that the decision by Ravec had not been irrational or procedurally unfair.

King Charles III shaking hands with Prime Minister Giorgia Meloni.

King Charles with Giorgia Meloni, the prime minister of Italy

REX

Now, the duke’s barrister, Shaheed Fatima KC, was back to argue that Harry’s life was “at stake”. A source close to Harry said: “The case is extremely important to the duke, evident by the fact that he attended both days in court.”

Back in Rome, there was a European shrug and an eye roll from those close to the King. The court case had been a “frustration” to the King for some time and a key reason given as to why Charles felt unable to meet his son.

Harry’s insistence on “suing the King’s government, in the King’s court” was bad enough. That the duke, 40, made it clear that he felt his father should intervene on his behalf was considered absurd. That it was now threatening to overshadow a serious government mission to bolster relations with a key European ally in a post-Brexit world was aggravating.

Some pondered whether Harry’s appearance in court might not have undermined his very argument; if he was so worried for his safety in Britain, why travel to a court hearing that you could just have easily followed from the comfort of your Montecito mansion? And while Harry was clearly not able to choose the date of his court case, the timing was rather less than ideal.

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Few events in the royal calendar raise a courtier’s blood pressure as much as a state visit. As well as the logistics, the two governments work together for months in advance to thrash out a deal, such as a new trade agreement.

A source said: “Nothing happens for nothing on a state visit, there is always something each country wants to get out of it and it has to be a done deal before you get anywhere near a red carpet.” In other words, the stakes were high for the King this week too.

When he became the first British monarch to address both Italian houses of parliament on Wednesday, Charles said that he was there “with one purpose — to reaffirm the deep friendship between the UK and Italy”.

While his younger son was arguing that the taxpayer-funded police should accompany him on every trip to the UK instead of the “bespoke” package he receives, the King was meeting Italy’s president and was viewing a colourful flypast of the Red Arrows and their Italian counterpart, Frecce Tricolori, over the skies of Rome.

On Thursday night it was revealed that Harry, the man who fears for his life in Britain, had made an unannounced trip to Ukraine as part of his work with wounded veterans.

Even Harry will know this would garner some much-needed positive publicity, although he may not have considered the impact on his father’s final farewell to Italy.

Intriguingly, it emerged that Harry was in Britain before the King had left for Italy, raising the prospect that there might have been a father-son reunion. The King’s helicopter landed at Kensington Palace in London on Sunday. Might this have been a moment for Charles to see the son he hasn’t met since the King’s cancer was diagnosed in February last year? In a word, no, according to a Palace source.

The chopper was a means of getting the King into the capital for cancer treatment — administered early to allow him to go ahead with the visit to Italy unimpeded. So, no time to see his son before jetting off to Rome the next day. Or rather “Harry-vederci”, as The Sun headline put it.

Yet far from being a mere frustration, the outcome of Harry’s case, when it comes, could have a bearing on what relationship, if any, the King has with his younger son in future.

As time goes on, it seems less likely that Charles will ever have much meaningful contact with his son and daughter-in-law. Harry’s children may grow up never knowing their royal grandfather — or their other one, but that’s another matter — beyond what they see in the news.

The duke now lives in California, where he seems to have a portfolio of bit-part jobs while his wife steams ahead with the launch of her lifestyle brand, As Ever. Meanwhile, the King is in a hurry. He knows the speeches on state visits are the legacy-making moments for which he will be remembered long after he is gone. As Charles says himself, he doesn’t know how long God plans to keep him in the job.

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Harry is also conscious of this. In his autobiography, Spare, the duke said that his father had urged his sons to make peace, telling them: “Please boys — don’t make my final years a misery.” Harry added: “His voice sounded raspy, fragile. It sounded, if I’m being honest, old.” All the more reason, then, to make amends.

The Palace is looking to see what a verdict could mean for future relations between the King and Harry. If Harry wins the right to automatic police protection for every visit, would he want to return to the UK more often? Would Meghan?

On the other hand, if he loses his long and costly court battle (those billable hours must be racking up), could Harry find that he has painted himself into a corner? He has said that it is not safe for him to bring his children to Britain. If so, there may be no hope for the King to see his grandchildren Archie and Lilibet.

On the final day of his state visit to Italy, Charles turned to speak to members of the embassy who had gathered to watch him plant a tree in the gardens of the British ambassador’s residence in Rome. The King quipped: “Well, I do hope that I shall live long enough to see a little bit of growth in the tree.” He may well feel the same way about his American grandchildren.