Cometh the hour, cometh the comedian disguised as an Israeli anti-terrorist expert. After Borat and Bruno, arch prankster Sacha Baron Cohen had declared himself done with the fake interview format that made him famous. But dark times call for radical measures, which is why he has just unleashed the ultimate anti-Trump satire in Who Is America?, a scorched-earth chuckle onslaught in which the comedy is dark and the anger is electric.

That Who Is America? is more than an exercise in rib-tickling is made obvious at the outset. The credits hopscotch from John F Kennedy and Franklin Roosevelt, delivering his “nothing to fear but fear itself” inauguration address... to Donald Trump mocking a disabled reporter. How quickly, terribly, the land of the free has slipped.

But Who Is America? suggests this decline and fall is a long way from striking rock bottom. In episode one, in the prosthetics-plastered guise of ex-Mossad man Erran Morrad, Baron Cohen persuades pro-gun advocate Philip Van Cleave into participating in a public information video for the fictional “Kinderguardian” programme, by which children as young as four would be trained in fire-arm use to ward of school shooters.

“To feed him, take his lunch box and push it into his tummy like this,” says Van Cleave in the bit, pointing his “puppy pistol” at the camera. “Just remember to point Puppy Pistol’s mouth right at the middle of the bad man. If he has a big fat tummy, point at that.” That rumbling noise is your stomach churning while your head explodes.

“A three-year-old cannot defend itself from an assault rifle by throwing a Hello Kitty pencil case at it,” adds Representative Joe Wilson of South Carolina, whom Baron Cohen likewise rounds up for his video. “Our Founding Fathers did not put an age limit on the Second Amendment.”

“The intensive three-week Kinderguardian course introduces specially selected children from 12 to 4 years old to pistols, rifles, semiautomatics, and a rudimentary knowledge of mortars,” says the former congressman and talk-radio host Joe Walsh. “In less than a month, a first grader can become a first grenader.”

“Toddlers are pure, uncorrupted by fake news or homosexuality,” contributes Larry Pratt, the executive director emeritus of Gun Owners of America as the sequence plunges further down the rabbit-hole, to a place darker and scarier than mere satire.

“Children under five also have elevated levels of the pheromone Blink-182, produced by the part of the liver known as the Rita Ora. This produces nerve reflexes to travel along the Cardi B neural pathway to the Wiz Khalifa 40 percent faster, saving time and saving lives.”

After the episode some of those involved came out with hands raised - yes they’d been duped...duped good.

“Do I believe kindergarteners should be armed?,” tweeted Walsh. “Hell no. But, it's on me. Sacha fooled me good. Flew me out to DC for some made up friend of Israel award. I gotta live with it.”

Presumably in the name of balance - and to deflect the charge of being aboard some left wing media bandwagon - Who is America? also pranks liberals...though here the punches fail to connect. Bernie Sanders is by turns reasonable and justifiably exasperated in conversation with Baron Cohen’s version of an Infowars-style conspiracy nut; former newsman Ted Koppel, after confronting the interviewer with cold, hard facts, cuts short the interview.

What’s most striking, though, is that rage, not humour, is the show’s primary emotion. Baron Cohen never steps from behind his mask yet you can tell he’s broiling with anger over America’s lurch into Trump-ian insanity. The strength of his feelings - which burns through the screen on Who Is America? - is connected, it is tempting to conclude, with his family history, which includes a Jewish grandmother driven from Germany by the Nazis, and who would later find fame on YouTube as a 99-year-old exercise teacher.

Given his family’s own experiences of fascism, it’s probably no surprise that Baron Cohen should feel strongly about America's slide towards the right. In one of his few in-depth interviews, he told podcaster Marc Maron that the road to extremism was shorter than generally assumed.

“There was this one major historian of the Third Reich, Ian Kershaw,” Baron Cohen said. “And his quote was, ‘The path to Auschwitz was paved with indifference.’ I know it's not very funny being a comedian talking about the Holocaust, but I think it's an interesting idea that not everyone in Germany had to be a raving anti semite. They just had to be apathetic.”

However, it’s also clear that, for all his unquestionably genuine high-mindedness, Baron Cohen gets a kick out of pranking politicians, celebrities and anyone with an extreme viewpoint.

Twenty years into his career, he’s still taking the same risks. The difference is that today it's the people opposite him, rather than Baron Cohen’s own creations, who are the truly unhinged ones.

Who Is America? continues on Channel 4 on Mondays at 10pm.