“The first question people were asking me was, Did I know anything about it? And the answer is no, absolutely not. I probably wouldn’t have bothered writing an episode of a fictional comedy-drama if I’d known. I’d have been running around screaming it into traffic. It’s a complete coincidence, albeit a quite bizarre one.”

Black Mirror poster. Photograph: Channel 4

To fill you in: four years ago, Charlie Brooker’s dystopian TV series Black Mirror began with an episode called the National Anthem, in which the prime minister of Britain – to hoots of derision on social media – is required to have sex with a pig on television in order to ransom a kidnapped princess. On Monday, the Daily Mail printed extracts from Lord Ashcroft’s biography of David Cameron, in which Ashcroft claims to have been told by a current MP that Britain’s real prime minister allegedly “inserted a private part of his anatomy” into the mouth of a dead pig during an initiation ceremony while he was studying at Oxford. The MP knows someone with photographic evidence, according to Ashcroft, but he does not supply any.

For Cameron, whether or not the allegation is true (Downing Street have refused to comment), it must be unspeakably embarrassing. For Brooker, it is just deeply, deeply weird. Indeed, when the story broke, and his phone went crazy, he was just sitting down to work on another dystopian script idea. “I did genuinely for a moment wonder if reality was a simulation, whether it exists only to trick me. Which isn’t meant to sound narcissistic,” he says. “It’s just a bit of a worry.”

According to Brooker, the real origins of his pig storyline are the media frenzy that followed Gordon Brown’s “bigot” remarks in 2010, and an edition of the Fabulous Furry Freak Brothers comic, in which, as he remembers it, a police chief is required to have sex with a hog. The comic itself may have picked the idea up from what seems to be a standard piece of political wisdom, attributed by Hunter S Thompson to Lyndon Johnson, in which a politician smears a rival by falsely “calling him a pig-fucker” in order to “make the sonofabitch deny it”.

While developing Black Mirror at Channel 4, Brooker remembers exploring alternatives to pigs. “We thought all through the farmyard,” he says. “At one point we were thinking of a giant wheel of cheese. Then we came back to the pig … You needed something that straddles the line between comic and horrifying. ”

Even so, Brooker has quite a record of at least seeming to be clairvoyant. Nathan Barley, the sitcom he made with Chris Morris in 2005, now looks like a straight-faced preview of iPhones, selfies, YouTube and hipsters. Just a week ago, G Clay Whittaker made similar claims of prophecy for various Black Mirror episodes in the Daily Beast – with the exception of the pig episode. “I’m not going to compare any political event to this,” he wrote, wrongly, it now seems.

For his part, Brooker says that he never seeks to make predictions in his scripts, even if he ends up doing so. What makes this case so strange however, is that he actually tried to do the opposite in the National Anthem – to think up, as he puts it, “an absurd and ridiculous notion”. Today, he insists he actually feels quite sorry for Cameron. “In the episode itself,” he says, “it’s worth pointing out that it doesn’t actually damage the prime minister in the long run.” At least Downing Street’s communications team can cling on to that.