Harry, Duke of Sussex, has squandered chance to become a great influencer - David Behrens

Just as the Duke of Cambridge was taking his seat at Westminster beside his father as kings in waiting, his errant brother was popping up in a “comedy video” wearing jogging bottoms and a T-shirt emblazoned with the words Girl Dad. It was his idea of a joke, apparently.

It was certainly a more casual form of fancy dress than that worn by Charles as he delivered what will be the first of many sovereign’s speeches to parliament.

But it illustrated just how entrenched the cultural chasm between his two sons has become; William following dutifully behind his dad and then going to the opening of the Manchester Arena bombing memorial to deliver a respectful address; Harry camping it up for no apparent purpose but his own amusement.

It must seem exasperatingly familiar to the few who remember the 1930s, for this is Edward and Wallis Simpson all over again; an abdication tale for the Twitter generation.

The purpose of Harry’s self-indulgent video shoot in New Zealand was ostensibly to promote his “sustainable tourism initiative”, Travalyst, which rates holidaymakers rather than travel firms according to their green credentials.

This is a bit rich coming from someone who used a private jet last year for a two-hour flight home to California from the skiing resort of Aspen. A T-shirt with the word Hypocrite plastered across the front would have been a better joke.

It has taken just four years – for this is his anniversary week – for the Duke to shrink from a privileged position as one of the world’s potentially great and genuine influencers into the type of self-appointed spokesman who posts unboxing videos on YouTube. Seldom in history has so great an opportunity been so badly squandered.

Next month, his ignominy will be complete as he watches from the sidelines when his father and brother wave to the Jubilee crowds from the Palace balcony. Harry and Meghan – the American divorcee for whom he gave it all up, just as his great-great uncle had done – will be lucky if even Prince Andrew bothers to speak to them.

We might not have to hypothesise about this, because following in their wake will be a film crew making a Life with the Sussexes reality show for Netflix – a kind of Geordie Shore, with cucumber sandwiches. William is reportedly worried that any private conversation with his brother will find its way into it.

Meghan, meanwhile, is said to be planning another damage limitation interview with Oprah Winfrey, to counter claims that she hated every second of her Royal visit to Australia and the South Pacific after her wedding.

The formality, she apparently thought, was “dated”, which indeed it was. So was Tuesday’s procession of the imperial state crown to parliament in its own limousine. But isn’t that the sort of pomp Americans are supposed to love about us?

The fact that she has “given up on Britain”, according to the biographer Tom Bower, makes her as out of step with her own people as she is with us.

And in courting publicity on her own terms she is treading old ground, for that was exactly what Wallis did after the original abdication crisis; she and Edward were only too happy to sell interviews in the mansion they shared on the Bois du Boulogne.

Yet in some ways, Harry’s betrayal of his country is worse than that of his ancestor, for while he did not have to give up the throne, he wasn’t made to go without anything else, either.

He was allowed to marry the woman he loved, and both she and he were given a platform from which they could inspire real change. Even by current millennial standards, you have to be very self-absorbed indeed not to see that as a golden ticket.

The next House of Windsor – the one laid out for us on Tuesday – will have its own challenges, for after so long as heir apparent Charles may find his people newly ambivalent about the continuing need for royalty at all. But there will be no doubting the hostility among us towards a Duchess who ducked her duty.