Simon Amstell has long been a provocative presence on our screens. “The British comic has a gift for taking a social norm and gently mocking it until it seems utterly ridiculous”, observed the New York Times back in 2012. His latest project, a feature length mockumentary, has turned this into an art form.

“Set in a utopian 2067Carnage looks back at a time when human beings ate other animals. For the young people of this time, the idea that their grandparents could have been complicit in a bloodbath of unnecessary suffering is wholly unimaginable” says the BBC.

“The film aims to break the taboo around Britain’s animal eating past, whilst showing compassion for a generation, now seeking therapy to cope with the horror of their unthinkable actions” and “gives a unique comedic peek into the future where animals live equally amongst humans”

Tuesday’s Premiere at the BFI was an upbeat affair, full of friends, family, collaborators, fans, and journalists. The woman next to me, from Chortle (the comedy website), laughed raucously from the start but gradually grew more subdued.

It was an unsettling watch, this curious mix of comic drama, archive footage, fake documentary clips, puppet shows, interviews and faux news reports. At times it was hard to know what was pretend, and what was real. Aside from the clips of animal abuse (deployed minimally). The commentary, courtesy of Amstell himself, is hilarious and hardcore. “Fisting cows” he cries. By the time it ended, I thought Carnage was the most subversive thing I’d seen since Brass Eye. Brass neck in Amstell’s case – for boldly taking Sci-Fi where no-one else dare.

In the Q&A after with film critic Mark Kermode, he reveals he went vegan after seeing Earthlings, but found that others wouldn’t watch the film as it was too upsetting. “So I thought it would be a good idea to make something funny and watchable, so that the message could be put across in a way that didn’t traumatise people”.

“The compassionate angle” he says, is the film’s “saving grace”. That’s true, I think: for although the joke is most definitely on us (carnists and vegans alike), it’s handled in a way that retains our collective dignity.

The master stroke was setting it in the future, allowing him full creative licence. A surreal scene is a clip from a (fictional) opera, featuring actress Samantha Spiro dressed as a cow and singing lines like “Why did you take my baby?” Writing this song “from the perspective of a cow” is the thing Simon’s most proud of: “When Sam sung it, we were doing a close up, and she actually made me cry”. Kermode concurs: “Actually, that song is starting to get under my skin and in a really bizarre way”.

Carnage is a fiendishly clever name – part reference to Carnism, the name psychologist Melanie Joy coined for the prevailing meat-eating ideology.

“This revolution is happening now, whether anyone likes it or not”, says Amstell. “I think that’s why I felt as long as it’s funny. You just have to be funny. Ultimately, it’s going to be really awkward if we keep eating other animals”.

Carnage isn’t the first funny film about veganism (see Truth or Dairy starring Benjamin Zephaniah), but it is on another level.  As I sat in the Bar afterwards nursing my third Coconut Daiquiri – I couldn’t help but chuckle, and shake my head, thinking: wow, did that really just happen?

Watch out World, Carnage hits BBC iplayer on 19th March