Prince William and Kate Middleton clearly have many sterling qualities – he’s done yoga in a white jean, she can sail and take photographs while maintaining her blowout – but until now they haven’t showed much of a sense of humour.

That all changed when they toted their children Prince George, Princess Charlotte and Prince Louis on a budget flight to Scotland on Thursday.

The photos showed the novelty trip to be much like everyone’s when they’re juggling kids, boarding passes and luggage. William wore a dad jumper and shepherded his two eldest while Kate trailed behind with Louis on hip (and what appeared to be a minion bringing up the rear.)

The funny and fascinating bit was that the Cambridges, to my eye, were having a sly and quite hilarious dig at Meghan Markle and Prince Harry.

It surely can’t be coincidence in a week when eco-warriors the Sussexes were canned (by media and the public) then defended (by Elton, Ellen and Pink) over their private jet habit that the Cambridges show up in the $132 seats at a local airport.

The contrasting visuals were fabulous.

In the red corner, there’s Harry and Meghan stepping off Elton’s private plane in the south of France with a blanketed hidden Archie in arms, ready to be whisked to the singer’s ostentatious private villa.

In the blue, we have William and Kate with kids trundling across a tarmac in full view. George wasn’t even in his traditional old-school getup but rather his more modish new favourite polo top like a normal boy.

Kate follows the family while carrying baby Louis. Photo: The Daily Mail

Not for the Cambridges some sun drenched afternoons by the pool with the Rocket Man (although they did reportedly go to Mustique recently, so they don’t mind a high end tropical getaway.)

No, they were off to Granny’s place at Balmoral for some fly fishing and bracing walks and card games, as William and Harry have done since they were born.

Prince Charles with young sons William and Harry at Balmoral, Scotland. Photo: Getty

This is a trip William and Kate have made countless times but the first one they’ve done by low cost airline instead of jumping in the Range Rover.

There’s possibly two strategies at play here.

For mine, the main message is that this is the early version of Kate’s reportedly traditional ‘joke’ Christmas gifts to Harry. In 2011, for instance, she is said to slipped a ‘grow your own girlfriend’ kit under the tree for him.

William and Kate are having a laugh at the Sussexes.

Hey guys, we’re the ones who really count, who will one day sit on thrones, but we’re happy to slum it with the people while you travel and holiday like Hollywood royalty.

That last part is the serious bit of the whole Windsor image wars.

The Queen knows better than anyone that the royals have to tread a fine line between being above everyone by dint of birth or marriage, but not better than them in terms of what should be gained from a life well lived.

Meghan and Beyonce’s rapturous greeting at July 14’s The Lion King premiere. Photo: Getty

She’ll be aware that Harry and Meghan’s combined persona is so far a slightly uneasy mix of the worthy and the glittering. Saving wildlife and sex workers one day, kissing Beyonce and Jay Z the next.

Undeterred by clapback over her British Vogue September issue, Meghan released an Instagram story heralding the release of her clothing collaboration with charity Smart Works.

There’s the duchess styling women, checking out footage and laughing, to the tune of Bill Withers’ Lovely Day.

It’s quite charming and deliberately artless, and utilises Meghan’s professional comfort in front of a camera.

Kate – who has said she hates public speaking – doesn’t have the same talents at her disposal, which is why it was a smart move to cede the showbiz stuff to her fellow duchess, and take to the cheap skies instead.

All up, it’s been a satisfying demonstration of the royals playing to their strengths in a spot of inter house PR sport. Kate and William take the trophy this round.