Five days after a top executive of Huawei, the Chinese telecoms group, was arrested on a US request in Canada, President Donald Trump said he was willing to intervene — if it helped secure “the largest trade deal ever made”. The detention of Meng Wanzhou, one of China’s best known executives, was undoubtedly an incendiary step, escalating trade tensions with Beijing. But presidential interference in the case would send entirely the wrong message about the US justice system — and about how the administration conducts international affairs.

The US and western allies have legitimate concerns about China’s reputation for digital espionage and theft of intellectual property. They agree a more robust stance is needed towards Beijing. But arresting a star of Chinese business — Ms Meng has been called China’s Sheryl Sandberg — on a Canadian stopover en route to Mexico from Hong Kong is not the way to persuade Beijing to change its behaviour.

Even if the Huawei chief financial officer was held on unrelated charges of violating US sanctions on Iran, the move smacks of using individuals as pawns in negotiations. It is seen in Beijing as Washington rewriting the rules of engagement. Such waywardness and unpredictability from a country that used to portray itself as a pillar of the international rules-based order will tempt China to respond in kind, leading to a downward spiral of tit-for-tat behaviour. Indeed, the detention of a former Canadian diplomat, Michael Kovrig, in Beijing looks worryingly like retaliation.