To understand the current political frenzy on both sides of the Atlantic, it helps to know Tortuous Convolvulus. Unfamiliar with his work? Convolvulus was a spy, operating around 50BC, a specialist in psychological warfare. He was deployed by Julius Caesar against a stubborn Gallic rebellion, and his methods were not so different to those of Russian cyber-saboteurs against western democracies.

On a recent trip to the US I was struck by how engaged officials were with the question of a Kremlin-sponsored Brexit

It is worth adding that Convolvulus is a character from Asterix and the Roman Agent, a book known to most English readers in translation by Anthea Bell. The sad news of Bell’s death last month triggered many fond memories and one association with current events: the devious Roman provocateur who initiates a conspiracy theory about Asterix leaking the formula for the magic potion that allows the Gaulish village to defy Caesar’s garrisons. The fake news breeds mistrust and the villagers’ solidarity collapses.

That Convolvulus is a fictional character doesn’t diminish the relevance of his techniques. The point is that there is nothing new in disinformation, and no strategic genius in a campaign to destabilise societies by aggravating their divisions. It is cartoon-level espionage, simple but effective.

The fact of Russian meddling in the 2016 United States presidential election is not in doubt. The scale of complicity with the Trump campaign should soon be revealed by special counsel Robert Mueller. In the absence of an equivalent investigation in Britain, it is hard to know how much energy the Kremlin has put into influencing our own politics, but there are no prizes for guessing which side Vladimir Putin rooted for in the Brexit battle. Maybe Leave.EU’s Arron Banks was invited to boozy lunches in the Russian embassy, and offered privileged access to goldmine investments because of his amiable manners. It is likelier he made the guest list as a financier of anti-EU propaganda.

‘Maybe Leave.EU’s Arron Banks was invited to boozy lunches in the Russian embassy and offered privileged access to goldmine investments because of his amiable manners.’ Photograph: Mark Thomas/REX/Shutterstock

On a recent trip to the US I was struck by how engaged diplomats and former government officials were with the question of a Kremlin-sponsored Brexit. They saw compelling parallels with the torpedoing of Hillary Clinton’s White House bid, and were surprised that the story was not getting more traction. The New York Times has given it more prominence than most UK media. One report said London was “grappling with whether Moscow tried to use its close ties with any British citizens to promote Brexit”. That was misleading to American readers. There is no grappling.

Some Labour MPs have called for a Mueller-style inquiry in Britain, but their boss is uninterested. Giving Moscow the benefit of the doubt is basic foreign policy for Jeremy Corbyn and his closest advisers. Could his last general election campaign have been given a comradely boost by Vladimir Putin’s digital battalions? And, with Kremlin apologists in the room, the opposition leader’s office doesn’t have much incentive to demand that spotlights be shone on nefarious Russian influence.

Theresa May is not shy of denouncing Putin as an aggressor against the west, but she never dares to suggest that UK democracy might have been hacked. She lacks the energy and courage to face the logical follow-on proposition: a compromised referendum means a less compelling mandate.

It is not surprising that Brexiters belittle the suggestion that their project of national liberation was hijacked in service to a foreign power. It is also frustrating when remainers use that idea as a crutch. A few roubles and robotic tweets could not account for 17.4 million people rejecting EU membership, even if they lubricated the argument a bit. Some perspective is required. No Kremlin laboratory cooked up the socioeconomic frustrations that boiled over into Brexit, nor did Putin synthesise the racial animosity pumping around parts of white America to fuel Trump’s campaign.

The sinister image of the master-manipulator cyber-cephalopod with tentacles that cross continents flatters the Russian president. He is a political gangster running a dysfunctional state for whom vilification abroad can be useful in burnishing his credentials as the strongman at home. The key question is not whether meddling tipped the balance for Brexit or Trump, since that is unquantifiable, but what in those campaigns suited Russian foreign policy goals.

The common thread is division: fracturing the western alliance and prising open social fissures in the domestic sphere to make states less governable and thereby weaker. The Convolvulus doctrine is not interested in dictating specific outcomes so much as sowing discord for its own sake.

The job of disinformation is not to promote one set of facts over another, but to disorient and inculcate a nihilistic suspicion of all news, undermining confidence that the truth is available at all. And the function of weaponised trolling online is not to advance an argument but to provoke a red mist of rage and mutual suspicion that impedes judgment and drowns out moderation. The social media bots leap into action after dramatic, emotive events – terrorist attacks, for example – to boost both sides in a controversy. The purpose is not to win but to polarise and radicalise everyone in the conversation.

The French title for Asterix and the Roman Agent is La Zizanie – a barely translatable word combining strife and confusion. It is the state of British politics flailing around in its Brexit quagmire.

The health of a democracy can be measured in its capacity to host civil public disagreement. The toxicity of la zizanie is not intensity of debate but its conduct without rules. It is the corrosion of that unspoken sense of common social enterprise that distinguishes an argument from a brawl. It is contempt for the idea of neutral institutions, dispassionate analysis or valid criticism in the media. Everyone is either with you or against you. It is the presumption that the other side is not just wrong but wicked; that their motives, not just their arguments, are bad. It is hard to defeat democracy by running against it in a fair campaign. Instead, its enemies succeed through degradation of political culture, until elections are not a business of persuasion but of conquest; not winning the vote but crushing the enemy. It is a descent into the kind of venomous, corrupt, lie-infested and cynical power games that I saw consume Russia’s fragile post-Soviet democracy when I lived in Moscow. It is not a style I would recommend importing to Westminster.

• Rafael Behr is a Guardian columnist