I’d like to say that he was wearing a mask and a cloak, and that we met in the bowels of the Her Majesty’s Theatre, but the truth is more prosaic: beanie hat, hoody, an arterial road in London. This, sadly, is the lair of the Phantom fan who has led the internet crusade against Andrew Lloyd Webber’s latest musical. Or to use his own description: “I am the mastermind behind the guerrilla campaign to destroy Love Never Dies.” That’s more like it.

Yesterday I tracked down the man who prompted the vicious online verdicts that preceded the opening. Why has he taken on the mighty Lord, I asked, and he indulged me with an exposition longer than several arias. The gist is that the events in Love Never Dies could not have followed Phantom, whose protagonist dies in Gaston Leroux’s early 20th-century gothic tale on which which the musical is based.

“The sequel makes zero sense and contradicts the whole point of the original,” says the man we’ll call Gaston. “So in November I set up a Twitter and Facebook group against it as a complete joke because there didn’t seem to be any platform for fans who know the story really well. We’re up to about 800 people now, and critics’ inboxes have been inundated with our views. Lloyd Webber has underestimated the intelligence of his audience.”

So Gaston’s complaint is an artistic one? “Phantom is the creation of a French author and his estate is against the sequel,” he replies. “But because these days Phantom is associated more with Andrew Lloyd Webber there’s a fear that this sequel will be taken as canon and that future generations will think this is how the story was supposed to continue. We don’t want to see that happen, and we don’t want to see the show pulled through the mud.”

Gaston is young, highly educated, professional and earnest. Paranoid, too, that the barminess associated with Phantom fandom would not enhance his budding career — hence his insistence on anonymity. He has a point. He has seen Phantom 40 times in venues around the world. “Lloyd Webber’s strategy is to dismiss fans’ opinions, to say that they’re obsessed and sad. I certainly don’t go and see Phantom in costume, weep copiously and buy another ticket on the way out,” he says.

Gaston has no plans to see Love Never Dies. “I think I’m quite within my rights to judge something when I know the entire story and have heard the entire score. We’re not trying to close the show, but to correct the laziness of the assumptions that fans are happy with the sequel, that we’ve been waiting for it. That’s what riled people. Job done, I think.”