When Donald Trump was elected president in 2016 one of his first big breaches of convention was highly technical — he took a congratulatory call from Tsai Ing-wen, then the president of Taiwan.

In the world of diplomacy, this was an earthquake. No American election winner had done that since 1979, when Washington belatedly recognised the Communist Party regime in Beijing. The Communist Party regards any suggestion that Taiwan is a “normal country” as offensive.

In the world of geopolitics, it marked out the Trump administration as China’s biggest foe in the White House, and Taiwan’s biggest friend, for decades. This time around, all that has changed, to a degree that is causing unease in Taiwan just as China’s navy is circling the island, sometimes