The French president, Emmanuel Macron, never ceases to surprise his audience, especially when he speaks in English. While some of his compatriots were shocked that he should address the US Congress in its native tongue, it pleased a large number of French people who appreciated how he engaged directly in version originale.

A few days later, however, when President Macron thanked the Australian prime minister’s wife, Lucy Turnbull, for being “delicious” – conjuring up images of cannibalism and Hannibal Lecter – some commentators suddenly thought of Macron as creepy. It was hours before somebody thought to tell the Australians that the word “délicieuse” actually means delightful.

Lost in translation: Macron thanks Australian PM's 'delicious' wife Read more

Speaking a foreign language is a minefield for anyone who ventures there but also a source of constant wonder, joy and fun. The rewards are manifold and it is even thought to prevent Alzheimer’s disease.

The smartest leaders either know many languages or understand the power of words enough to play with them to their advantage. Perhaps Macron used the word “delicious” on purpose; perhaps, even, the secret behind the strangely warm rapport between Macron, Trump and their wives is built on such deliciously faux amis?

The fact is that multilinguists rule the world. That Angela Merkel is trilingual (she speaks German, Russian and English) should be no surprise. If David Cameron had not been a monoglot, maybe Britain would not have found itself in a Brexit nightmare. Just a thought.

I will always remember when Yasser Arafat, the leader of the Palestinian Liberation Organisation, on a visit to Paris in 1989 declared in French on French television that the PLO’s charter was “caduque!” What a stroke of genius. The world reached for their French dictionaries and discovered Arafat had just buried the 1964 Palestinian charter (since “caduque” means out of date), which had so far insisted that armed struggle was the only possible way to win back the homeland. This tiny word paved the way to the Oslo accords of 1993 and the famous handshake between Arafat and Yitzhak Rabin in Washington.

Play Video 0:19 Emmanuel Macron thanks Australian PM's 'delicious wife' – video

In 1940, Parisians owed a big favour to Louisa Gross née Horwitz, the mother of the then American ambassador to Paris, William Christian Bullitt Jr. A German Jew, she made sure that her son was perfectly trilingual, as fluent in German and French as in American English. When the French government fled Paris, in effect making Bullitt the provisional governor of the city, there were only a few hours left to save the city from the fate shared by Rotterdam and Warsaw. Bullitt managed to persuade two French officials to meet their German counterparts at Écouen, 12 miles north of Paris, to settle terms for the handover. With the document signed, the German Field Marshal Georg von Küchler called off the bombardment of Paris.

In everyday life, multilingualism and potential linguistic gaffes don’t carry such catastrophic potency, and faux amis leading to faux pas are part of the learning process. When I first arrived in Britain, aged 22, I found out that, more often than not, French words in the English language don’t actually mean a thing. I recall an awkward evening when an Englishman whispered some slightly salacious things to me. He winked and apologised for the “double entendre”. Double entendre? It took me some time to realise he meant “sous-entendre” – meaning implication.

It is, however, always better to make small mistakes like Macron did in Australia than to rely on poor translators. The writer Oliver Kamm, the son of one of the greatest living British translators Anthea Bell, reminded me this week that in 1977, the translator Steven Seymour, accompanying Jimmy Carter on an official state visit to Poland, had to be fired after a disastrous first evening. President Carter had begun his speech saying: “I have come to learn your opinions and understand your desires for the future.” His translator told the Poles, in Polish: “I have a carnal desire for Poland.”

• Agnès Poirier is the author of Left Bank, Arts, Passion and the Rebirth of Paris 1940-1950