SINCE the vote to leave the European Union, a striking number of Britons have exhibited symptoms of a new medical condition, “Brexit derangement syndrome”. BDS has afflicted some of the country’s most prominent figures. Lord Adonis, a former Labour minister, has argued that Brexit is “largely the creation of the BBC”. Alastair Campbell, Tony Blair’s former spin-doctor, took to the seafront in Brighton to blast out “Ode to Joy” on the bagpipes.

This week Bernard-Henri Lévy demonstrated that BDS is not just a British phenomenon. BHL, as he is known, styles himself as one of France’s leading public intellectuals. He sports expensive suits, white shirts unbuttoned nearly to the waist, and elegantly sculpted hair. He is regularly quoted on a wide range of subjects, from genocide to gastronomy. Brexit, he is convinced, will make Britain more insular and deprive the EU of its “liberal heart”. So far, so sensible. But BHL has also persuaded himself that he is the man to stop this popular revolt.

On June 4th at the Cadogan Hall in London he performed a one-man play called “Last Exit Before Brexit”. French was the most common language at the bar, followed by German. The few who spoke English did so with the plummiest of accents. The play consisted of a 90-minute monologue, culminating in the rousing peroration: “Please remain; yes you can; last exit before Brexit.”

The notion that a Frenchman standing on a stage in Chelsea and berating the British could change people’s minds about Brexit was always far-fetched. But BHL’s performance was even odder than this suggests. He played himself, in a hotel room in Sarajevo preparing a speech on Brexit. He strode around the room, called up images on his computer, talked to people on the phone (Salman Rushdie made a guest appearance), jumped fully clothed into a bath and spent the last half-hour soaking wet.

BHL served up a bit of red meat for his bejewelled audience, denouncing Boris Johnson, the foreign secretary, as a bigot (loud applause), proclaiming that Brexit would reduce Britain to a small island (louder applause) and calling for “the annulment of this disaster” (even louder applause). But he devoted most of the time to his hobby horses: Europe’s betrayal of the Balkans, the ugliness of euro notes (“Give us faces, not bridges!”), the excesses of the #MeToo movement, the wonders of his own hair, and his remarkable ability to make women go rigid during orgasm. It may not have been great drama, but it was the greatest example of BDS yet seen.