Sunday's episode of Last Week Tonight shared some shocking news about a well-known expert on the British monarchy. Indeed, host John Oliver revealed that royal wedding expert Thomas J. Mace-Archer-Mills is actually not British after all — something which the Wall Street Journal first reported on May 31. As it turns out, Mace-Archer-Mills' given name is Thomas Muscatello. Indeed, the British monarchy expert is actually an American who grew up outside of Albany, New York.

As Oliver described, Mace-Archer-Mills is the chairman of the British Monarchy Society. He frequently appeared on television ahead of Prince Harry and Meghan Markle's wedding in order to provide commentary on the upcoming nuptials. As The Washington Post noted, Mace-Archer-Mills' media appearances included some very reputable outlets in Britain, such as the BBC and The Economist.

Mace-Archer-Mills, 38, apparently first developed his British accent after learning it for an American high school production of Oliver!, according to The Post. He also reportedly befriended two elderly Brits when he was a teenager and has since referred to them as his grandmother and grandfather. Mace-Archer-Mills now lives in the United Kingdom and has applied for citizenship, but it is still pending, according to Vanity Fair.

Oliver appeared aghast at the revelation that Mace-Archer-Mills was actually an American — and also poked fun at his own Britishness when reflecting on the bizarre revelation. As the late-night host noted:

That's right, that British man is actually Tom Muscatello from New York. And that is a destabilizing thing to know. Because, if this guy isn't British, who the f*ck is? Am I actually British? Well, let me reassure you, my parents are listed in my phone as 'Mr. and Mrs. Oliver,' so I am definitely British.

Oliver then proceeded to point out the irony of Mace-Archer-Mills criticizing Markle and characterizing her as a royal family "interloper" when Mace-Archer-Mills has apparently created an entire aristocratic British persona for himself. The late-night host then played a clip of Mace-Archer-Mills condemning Markle for what he saw as seeking to upstage Kate Middleton, with the royal family commentator claiming:

You do not upstage the future queen of this country, especially when you're coming in the way you are. When you start to take the spotlight from someone like Catherine, and then you swoop into the United Kingdom — Here I am, the American — and you're wanting to really upstage the Duchess of Cambridge, the future queen — I won't have it.

In response, Oliver took Mace-Archer-Mills to task, asserting:

Oh, you won't have it, will you? You won't have it! Well, let me make this perfectly clear: Meghan Markle's American passport is not an insult to anyone. The name Thomas J. Mace-Archer-Mills, Esq., however, is insultingly British. That's the equivalent of a British person pretending to be an American and calling themselves, Jefferson Budweiser McNuggets Jr.

Mace-Archer-Mills has also criticized Markle and her Americanness in other media appearances, as The Guardian reported on May 31. For example, in a clip recorded outside of Buckingham palace, Mace-Archer-Mills said of Markle, “She is loud, she is American, she fights for her cause. We don’t do that here. ... We do things quietly with dignity."

Oliver wrapped up his segment by characterizing Mace-Archer-Mills' continued defense of his Britishness, even though he's been outed as an American, as a "bloody brilliant rubbish fire to behold." The host then proceeded to play clips of Mace-Archer-Mills asserting that he learned his accent through online courses and that speaking with a British accent now comes naturally to him.

Finally, Oliver noted that Mace-Archer-Mills' claim that he "knows more about the monarchy than most people in Britain" might "actually be true." And, as Oliver adamantly asserted, this claim should have "tipped everyone off ... because most British people, we don't care either way about the monarchy. That makes him clearly an impostor."