It started last year, when the two royal couples, formerly sharing a single Instagram account, split their social media presence.
And the accounts regularly appeared to go head-to-head, with posts just hours apart.
And on the last day of 2019, there was another undoubtedly unintentional but highly entertaining crossover.
First there was Prince William launching his Earthshot Prize climate campaign, and a few hours later there was younger brother Prince Harry giving baby Archie a cuddle.
Here, Beth Hale takes a look at the war of the poses.
Wills’ big announcement loses out to Archie’s cuddle
Prince William launched the ‘most prestigious environmental prize in history. Then, just as New Year’s Eve was nearing its end, up popped team @SussexRoyal with a minute-long video
There’s very little between the two royal teams and their Instagram presence. @KensingtonRoyal has a whopping 10.6 million followers, but newcomers @SussexRoyal are snapping at their heels with 10 million (they, did, of course have a good start: 8,000 followers within six minutes of the account being set up).
On the morning of New Year’s Eve, @KensingtonRoyal had a big announcement: Prince William launched the ‘most prestigious environmental prize in history’, in a bid to galvanise a decade of action to repair the planet.
The Earthshot Prize, endorsed by Sir David Attenborough, will grant millions of pounds to those who can come up with solutions to global warming.
So far 675,000 people have viewed the launch video, posted on Instagram on Tuesday morning, and a further 314,000 have liked a photograph of the prince, taken by wife Kate, at a glacier in the Hindu Kush mountains, in Pakistan. Then, just as New Year’s Eve was nearing its end, up popped team @SussexRoyal (who presumably had been in bed, given Harry and Meghan are said to have been enjoying a sojourn on Vancouver Island, Canada).
The post, a minute-long video of highlights in the couple’s year, ends with an image of Harry cradling his son Archie by a lake with the music of Coldplay playing as images roll.
The candid snap has father and son in co-ordinating shades of tan, each in woolly hats; Archie is wearing sheepskin boots gifted to them by the Australian Governor-General Sir Peter Cosgrove. Cute factor 10.
The couple wrote: ‘2019 in review. Wishing you all a very Happy New Year and thanking you for your continued support!’ And what a lot of support they have. The post racked up 260,000 likes in half-an-hour and, as of yesterday, had been watched 3.5 million times.
Back to nature on a difficult day
Back in September, the two Instagram accounts shared a post to mark World Suicide Prevention Day
Subject matter and tone can vary enormously on Instagram.
Back in September, World Suicide Prevention Day happened to coincide with the Duchess of Cambridge opening her Back to Nature play garden at RHS Wisley, alongside her baking chum and RHS ambassador Mary Berry.
No surprises in the collection of images posted by Kensington Royal — Kate in a floral dress, lots of very jolly children (not her own on this occasion) and Mary Berry. It garners a respectable 247,671 likes.
Over on @SussexRoyal, the young couple share a series of accounts of organisations that offer support to ‘ensure no one goes through a crisis alone’. No faces on show, but still 200,000 likes.
Head-to-head for the youth vote
A respectable 234,000 people liked @KensingtonRoyal’s post, a couple of hundred thousand less than those who admired the same day’s message from Team Sussex
Given the relative youth of the two royal households, it’s no surprise many posts focus on work with young people. And on October 22 they went head to head.
@KensingtonRoyal posted an image from Kensington Palace of the finalists from BBC Radio 1’s Teen Heroes awards, which recognises inspirational teens.
A respectable 234,000 people liked the post, a couple of hundred thousand less than those who admired the same day’s message from Team Sussex, showing Meghan with Canadian PM Pierre Trudeau, at the opening ceremony of the One Young World youth leadership charity.
Nothing beats father’s pride…
@KensingtonRoyal’s video coincided with the scheduled airing of an ITV documentary giving a behind the scenes glimpse of the Duchy of Cornwall, and gained 1.5million views
If anything comes close to pipping babies and children to the post on Instagram, it’s a love-in between a father and his eldest son.
To coincide with the scheduled airing of an ITV documentary giving a behind the scenes glimpse of the Duchy of Cornwall, @KensingtonRoyal posted a clip of a teary-eyed Prince Charles responding to hearing his son William carrying on his work.
The royals don’t often get so touchy feely, so it’s no wonder the video soon had 1.5 million views.
This easily outstripped the 455,000 likes garnered by a post the same day by team Sussex — a curiously unroyal missive wishing everyone a ‘Happy Halloween!’ It was accompanied by an image of the happy couple attending a special effects workshop while touring New Zealand; but really, who knew the royals even did Halloween?
… except Grandpa with the bonny babies
On November 14, Prince Charles celebrated his 71st birthday, an occasion both his sons were quick to mark with social media messages
Birthdays and anniversaries are always a good reason for an Instagram post. On November 14, Prince Charles celebrated his 71st birthday, an occasion both his sons were quick to mark with social media messages.
@KensingtonRoyal’s offering was a trio of images, the first a delightful snap of Prince Charles with Prince Louis in his mother’s arms.
Some 635,000 followers have ‘liked’ the post; impressive, but not nearly as many as have liked the post made on the same day by @SussexRoyal, a black and white image of Prince Charles looking down at his youngest grandson, Archie, cradled in Daddy’s arms on the occasion of his christening. With 921,000 likes, it’s a winner.
The icing on the cake
The video of Prince George has been watched 3.4 million times so far. Meanwhile, Harry and Meghan have been out of the limelight on their festive break
The cause can be as worthy as you like, but there is one surefire way to become an Insta-hit, and that’s to give followers a glimpse of the royal offspring.
So, as Christmas Day dawned, @KensingtonRoyal knew they had great footage with a video of Prince George mixing a Christmas pudding as William, the Queen and Prince Charles look on approvingly. It has been watched 3.4 million times so far.
Harry and Meghan have been out of the limelight on their festive break, and @SussexRoyal kept things low profile with a simple message of ‘wishing you all a very Merry Christmas’. A festive showdown with only one winner.
A Berry boost for the Cambridges
A whopping 433,000 have ‘liked’ @KensingtonRoyal’s snaps, while 2.5 million watched a second video post. On the same day, Harry and Meghan posted a missive about the importance of caring, but it got just 183,000 likes
It was a busy December for team @KensingtonRoyal, and on December 16 they came up with a winning recipe in the shape of Mary Berry. Shortly before appearing on BBC1 for the cook’s A Berry Royal Christmas, images of the couple with Mary appeared on Instagram.
A whopping 433,000 have ‘liked’ the snaps, while 2.5 million watched a second video post.
On the same day, Harry and Meghan posted a missive about the importance of caring. But it got just 183,000 likes.
All in blue to pay their respects
Prince Harry appears to have tipped the balance in favour of team Sussex, wearing his Army ceremonial uniform with his duchess in a stylish navy winter coat and hat at his side
Two duchesses in blue, one Prince in a suit, another in uniform. It was a close-run thing, but Prince Harry appears to have tipped the balance in favour of team Sussex, wearing his Army ceremonial uniform with his duchess in a stylish navy winter coat and hat at his side.
The picture, showing the couple paying their respects at Westminster Abbey’s Field of Remembrance on November 7, garnered nearly 500,000 likes.
On the same day, William and Kate also wore navy blue to attend the launch of the National Emergencies Trust, a charity providing an emergency response to disasters in the UK. This post received 377,000 likes.
Picture research: Claire Cisotti