As the world’s richest man Elon Musk likes to point out, he is a former holder of an H-1B skilled foreign worker visa for the US. So are Microsoft CEO Satya Nadella and Sundar Pichai, the Alphabet chief executive. Together these individuals run or have founded trillion-dollar businesses that have made a major contribution to US jobs and prosperity; a great American strength has long been its openness to foreign-born talent. All of which makes the Trump administration’s plan to impose a $100,000 fee for such a visa especially ill-conceived.

The move has exposed anew the divide between the techno-libertarians who helped finance Trump’s return to power and his Maga base. Curbing not just undocumented migrants but skilled worker visas is popular among his grassroots supporters, who see H-1Bs as favouring foreign workers and depressing US wages in key sectors. But many tech executives would like the H-1B system — currently capped at 85,000 a year for businesses, awarded via lottery — to be expanded. That the president has sided with his base shows the limits to his partnership with US billionaires — and that his populist instinct for splashy gestures, whatever the cost, can win out.

Silicon Valley uses H-1B visas heavily to hire foreign scientists, engineers and coders to make up for US skills shortages. Accountancy, finance and healthcare are also big users. Critics say hiring foreign workers more cheaply helps big business to keep costs down. But research has found that from 1990 to 2010, rising numbers of H-1B holders accounted for 30-50 per cent of all US productivity growth.