Shortly before George W Bush and Tony Blair launched their war, the Arab League issued a statement declaring that invading Iraq would “open the gates of hell”. Of all the pieces of intelligence that the CIA and British agents were gathering at the time, this turned out to be the only accurate one. The invasion was launched on “evidence” about weapons of mass destruction (WMDs) that consisted mostly of whatever it was Iraqi informants knew our intelligence agencies most wanted to hear and would happily pay for. The biggest contributor to this self-fulfilling dossier was an alcohol-fixated defector called Curveball, who later admitted his improvisations about chemical weapons weren’t true. No premise was too flimsy to get thrown on to the pile of spurious evidence. And before we knew it, that pile was big enough to justify sending our troops off into harm’s way. Many who made it home were broken for ever. At the time, I was numb with confusion and horror that the British democratic system could allow a prime minister, fixated on a threat people were telling him wasn’t there, to get his party and his opponents to back a war with no purpose, no target, no endgame and no rationale. We all told Blair at the time it wasn’t going to end well. Now here we are, 20 years later, and only half right: it did go as badly as predicted, but it hasn’t really ended. The war’s hellish reverberations are still being heard: on top of the human suffering, the rise of militancy, the collapse of markets and economies, the mistrust of the west and the transformation of Tony Blair into a haunted husk. One of the biggest casualties has been truth, which the war swiftly dragged out into the desert and left for dead. Post Iraq 2003, we simply don’t trust what our leaders tell us. How could this happen? My way of processing it all, and to try and attempt some sort of answer to that question, was to make The Thick of It. I wanted to know what exactly goes on behind those closed doors in Downing St and Whitehall ministries. How do some massively stupid decisions get made? The show wasn’t about Iraq: I wanted to cover the groupthink and moments of dysfunction that impact on government every day. I wanted to explain how the system gets us into those positions. But if The Thick of It wasn’t about the war, it was fuelled by my anger at it. If, among the comic one-liners and farcical plotlines, you hear a constant howl of rage and frustration in the background, that’s me. And I wanted you to hear it. By getting close-up to the dysfunction of power, my own set of creative priorities changed. I became less interested in the political personalities appearing on our screens, and more interested in analysing what they were saying. I wanted to catch them using language to distort meaning, or to distract us from a larger but less appealing reality. This was spurred by something Blair said in a speech to his party conference on 28 September, a year after the war. Seeking to justify the invasion, even though it had become clear the raison d’etre for the war, Saddam’s WMDs, didn’t exist, Blair said: “I know this issue has divided the country … I’m like any other human being – fallible … I only know what I believe.” It feels real, an appeal to the heart, an offer of vulnerability, but that phrase “I only know what I believe” is a false friend: it sounds casual but actually subverts the tradition of empirical inquiry we’ve been successfully using since Aristotle. Normally, if we have a hunch, we test it. If we’re looking for an explanation, we eliminate every available solution or possibility until we find the right one. On a day-to-day basis, to survive, we first believe what we know. Blair’s “I only know what I believe” is an unsuspecting admission that, for him, decisions are made primarily from gut feeling and a pool of emotions rather than from objective reasoning. This is perhaps understandable if you’re an arts minister and you want to guarantee some funding to a pet project, but it’s inexcusable when deciding whether to send men and women to their deaths. But it happened nonetheless, and we let it happen. And now, is it any wonder the past few decades have been defined by a politics that appeals more to our emotions than to any evidence of our senses? More and more candidates are chosen, and more and more leaders are picked, on the basis of belief rather than ability. More and more debates are neutralised into take-it-or-leave-it mantras that aren’t open to question: get Brexit done, the anti-growth coalition, stop the boats. This is a new emotional realm, where, in the words of Michael Gove: “The people of this country have had enough of experts.” Anyone who rails against this, who shows one iota of an appetite for facts and evidence, is lumped into catch-all categories of opponents: the metropolitan elite, the wokerati, the enemy within. This last one points menacingly at where we are now, 20 years later; in a land where criticism of the government in power is rebadged as treachery. Such are the booby traps that lie hidden in political discourse today; a landscape more littered than ever before with danger and lies. Armando Iannucci is a film and TV writer whose credits include The Thick of It, In the Loop and Veep