What will people in Republic make of the Windsors' newest couple?
As the Duke and Duchess of Sussex made the journey to the Republic of Ireland yesterday, Dublin-based writer Sarah Caden wonders how the Meghan effect will take hold throughout the world and whether she will be seen as the second Diana
According to the Cambridge English Dictionary, the definition of synergy is "the combined power of a group of things when they are working together that is greater than the total power achieved by each working separately".
In celebrity terms, synergy can work for a celebrity plus a brand (think Clooney and Nespresso) or for celebrity couples, who are even more powerful as a pairing than they were solo (think Posh and Becks).
In the case of Meghan Markle and the Windsors, it is as yet unclear how the celebrity synergy will play out, but this week's trip to Dublin might prove an indicator. Thus far, it seems an equally mutually beneficial meeting of new and old-world stardom, but that could easily shift. As Harry and Meghan launch themselves as a married couple on world tours, with Dublin part of a gentle introduction, how she wows the masses will start to set the tone for their partnership.
The manner in which Meghan manages herself on world tours could decide if she becomes Diana Mk 2, in terms of universal affection and super-stardom, or whether she settles into a role as Kate's also-ran sister-in-law.
We'd never been massively bothered Harry had never visited before and we'd hardly have been this excited about his impending arrival if Meghan wasn't with him. Certainly, she's the one Irish eyes hoped to glimpse.
Which is great for the fairytale so far. Actress of humble beginnings and mixed race lands a prince. Of course, the house of Windsor gains from this union too. The international attention paid so far to the story has been unprecedented and has mostly reflected well on the royals.
They've been so welcoming of Harry's choice of bride, a girl not only from America but from the world of showbiz too. A girl with a fractured family; a girl whose dad couldn't turn up for the wedding, thus allowing Prince Charles to gallantly rise to the occasion. They've been warm and modern and compassionate and all those things that for years - particularly after Diana's divorce from Charles and her later death - they were accused of lacking.
So far, the Windsors are the ones doing best out of the union, but that may simply be because Meghan remains in the rehearsal phase of making this new role her own.
At the moment, neither the royal family nor Meghan really have a handle on what they've entered into. She is, without doubt, nothing like Kate Middleton, who is the kind of girl that aristos can get their heads around. Much has always been made of Kate being middle-class, but all that really amounts to is that her parents don't have titles and earned their millions rather than inherited them.
She went to the right schools, met the right people and didn't end up with William through some sort of prince-and-the-pauper circumstances. They met because they had mutual toff friends and moved in toff circles at St Andrew's University.
Kate has also been on the Windsor scene since her late teens, so she not only grew up getting their world, but grew into adulthood adhering to the etiquette and arcane rituals.
The whole shooting match is a new world to Meghan Markle and her apparent nervousness at the public appearances she had made with Harry have probably partly been cluelessness. And the scrutiny, which isn't a feature of the rehearsal period of the acting world, is relentless.
In recent months, she has had the quality of her curtsies to the Queen picked apart; her hand-holding with Harry; the crossing of her legs in the Queen's company; her too-pale nude tights. No wonder the girl has, to date, looked ill at ease in public.
The scrutiny of her family hasn't helped, of course. Her father's appearance on Good Morning Britain, in which he commented on her marriage, was reported to have led her to believe that severing ties was the only answer to keeping the royal peace.
Then, only last week, one of Prince Charles's friends, designer Nicky Haslam, called the Markles "frightfully common. It would have been awful if that huge lump [Meghan's father] had been there. The royals probably don't quite know how to deal with them".
Well if we needed anything more to endear Meghan to us, the mere mention of "common" has done it. There's nothing we like more here than someone putting it up to the toffs.
Thus far, we warm to how she seems slightly ill at ease at royal events and get a bit of a giggle out of how Harry had to tell her to look up as planes performed a flyover at the recent Trooping the Colour.
Kate was like one of the Famous Five, marvelling as if she'd never seen an aeroplane before, but Meghan seemed sort of baffled by the fuss, as any of the rest of us would be.
And we welcomed Meghan this week as one of our own. There's Irish ancestry, apparently, but it's more than that. We have a simpatico with Meghan, while Harry, for all his modern openness, will remain other to us. Meghan, we get.
In the synergy stakes, everyone is doing well from the marriage of Meghan and Harry so far. As she learns the ropes and the role, however, Meghan remains something of the lesser partner. Her status is boosted by association with him, the balance of power still rests with her in-laws.
As an actress, though, she will quickly master her part and what we see this week, in the rather more relaxed environment of Ireland, might be the star that Meghan has been in her life before Harry.
She has, without doubt, an easy charm with people that we haven't seen since Diana and as she grows in confidence that may be the Meghan we see more of.
In truth, in time, it may become the case that the royals are really living in Meghan's world.