LONDON — Britain is in the grip of its most unrelenting heatwave in forever. The England national football team has made the semi-finals of the World Cup for the first time in 28 years, succumbing to Croatia on the eve of President Trump’s arrival in the capital. In a beer-fuelled, sun-drenched haze, the not-quite-state-visit of the Commander-in-Chief takes on an ever greater significance.

Having seen the full works laid on for Chinese premier Xi Jinping in 2015, despite his reputation and undemocratic consolidation of power in a brutal, corrupt leadership, and, earlier this year…