Meghan Markle and Prince Harry "married" three days before their Windsor Castle wedding ceremony, it was revealed in Sunday's bombshell two-hour interview with Oprah Winfrey.
The televised event saw 17 million people across the US tune in, according to preliminary data.
The admission has sparked confusion, however, as UK laws make this impossible.
In the first few minutes of the interview, Meghan revealed that she married Prince Harry in private, three days before their much-publicised 2018 Windsor Castle ceremony, which was watched around the world.
“You know, three days before our wedding, we got married," Meghan told Winfrey. "No one knows that. But we called the archbishop, and we just said, 'Look, this spectacle is for the world, but we want our union between us.'
"The vows that we have framed in our room are just the two of us in our backyard with the Archbishop of Canterbury," she explained, as Harry started singing "just the three of us", a reference to Bill Withers's song, Just the Two of Us.
The reason for the confusion stems from current English laws, which only permit couples to marry inside a place of worship or licensed non-religious venue. Two witnesses are also required to attend any marriage.
A couple are also unable to remarry each other, unless there is some doubt as to the validity of the earlier marriage, the rules state.
This means that if Meghan's claims are true, then the much-publicised marriage at St George's Chapel would have simply been a "spectacle".
This is seemingly impossible, however, as the UK Faculty Office tweeted a few days prior to the 2018 wedding that the registrar had "signed the Special Marriage Licence for HRH the Prince Harry and Meghan Markle to be married in St George's Chapel in Windsor".
It is more likely that the nuptials Meghan described were more of a blessing ceremony than a legally binding marriage.
Reverend David Green, Vicar of St Mary’s, West Malling and the Rector of St Michael’s, in Offham, took to Twitter to question the reveal.
"I’ve no idea what they mean. Obviously lacking as a parish priest," he tweeted while debating the issue with Reverend Tiffer Robinson of Suffolk.
"You can’t get married twice. So what was the thing three days before? And if it was a marriage, what on earth are we doing ‘playing’ at prayer / holy matrimony for cameras."
Robinson added: "She’s entitled to consider it her marriage if she wants to. Americans are much less concerned with the specifics of marriage law than English clergy.
“Most of their wedding ceremonies aren’t legal weddings … saying ‘we really got married three days before in a secret ceremony’ is not actually the same as saying they were legally wed three days before everyone thought they were.”
This thread has since been deleted.
Harry and Meghan's official royal wedding took place on May 19, 2018. At the time, the couple were living at Nottingham Cottage in the grounds of Kensington Palace.
Almost 18 million Britons watched the coverage, while 29 million people in the US tuned in.
A number of British and foreign royalty, international dignitaries and celebrity guests were in attendance, including Winfrey, Priyanka Chopra and Idris Elba.
