Anyone who doubted that King Charles was up to the most demanding royal job of all must surely be thinking again.

With confidence and charisma to spare, he has shown the world over the past few days how he could hardly be more suited to his role as monarch.

Even more importantly, Charles's assured performance during this week's State Visit to the US gave the strongest sign yet that he has at last stepped out from the very long shadow cast by his late mother.

No one should underestimate the stresses and strains surrounding the trip to America. Transatlantic relations have been under extreme pressure since Keir Starmer's initial refusal to allow US forces to use British airbases at the start of the war on Iran.

With some of Donald Trump's greatest admirers acknowledging that he can be a difficult customer even on a good day, it is hard to picture the King arriving into a more daunting scenario.

But Charles managed to walk a diplomatic tightrope with great aplomb.

Crucially, though, he also managed to speak up for Britain on a variety of potentially tricky topics in a considered and tactful manner. He employed old-fashioned charm and humour to devastating effect. 

Even his gift to the President – a bell from HMS Trump, a Royal Navy submarine launched during the Second World War – was inspired.

Truly, this was the royals' fabled 'soft diplomacy' at its best. It was also a masterclass by the King in how an awkward situation with our closest and most influential ally should really be handled. 

Needless to say, the PM's approach doesn't bear comparison. That ocean-going clunker began his relationship with Mr Trump on a note of extreme obsequiousness made no less embarrassing by the fact that it was transparently insincere.

Sir Keir's bowing and scraping gave way to petulance as soon as the request for help with the Iran conflict was made. His kneejerk, Left-wing lawyerly instincts kicked in and, without so much as a second thought, he needlessly alienated the world's most powerful man.

By contrast, the goodwill arising from Charles and Camilla's visit is already coming our way. Before they even arrived back on British soil, President Trump announced the lifting of the 10 per cent levy on exports of Scotch whisky to the US – a concession that months of negotiations by Starmer's ministers failed to achieve.

It is to be hoped that the huge success of the State Visit will also restore some of the monarchy's sparkle, which has been badly tarnished by Andrew Mountbatten-Windsor's antics and the painful rift with the Sussexes.

But the crucial thing for now is that a hugely important relationship that has just been through its rockiest patch for decades is back on an even keel.

No thanks to our hopeless PM for that. Instead, full credit is due to our 77-year-old monarch who was prepared to serve the nation's best interests by taking on a gruelling and difficult challenge – despite his ongoing treatment for cancer and a wife who famously dislikes flying.

Through the long decades before he ascended to the throne, Charles watched from the wings as Queen Elizabeth represented Britain on the international stage with utmost distinction.

Like us all, she would be very proud of her eldest son this week.