Donald Trump and Jeremy Corbyn should get together. Mr Trump wants to grab the Republican presidential nomination from the Neanderthal right. The would-be leader of Britain’s opposition Labour party hails from the hard, socialist left. They are seriously destabilising their respective parties. And they have more in common than either would care to admit.

The billionaire Mr Trump has leapt to the front of the GOP’s 16-candidate primary race for next year’s election for the White House. A poll released this week by the Washington Post and ABC gave him the support of 24 per cent of Republican and Republican-leaning voters. This for a candidate whose reactionary xenophobia can make the Tea Party sound liberal. On planet Trump, immigrants from Latin America and Mexico are rapists, criminals and drug-dealers, Senator John McCain is not a war hero because he was captured by the Vietnamese, same-sex marriage and abortion are anathema, China is an enemy and climate change a hoax.

If this has discombobulated mainstream Republicans, Mr Corbyn has stirred blind panic in the upper reaches of Britain’s opposition Labour party. Ed Miliband, the former leader, left his party in ruins after a crushing defeat at the hands of David Cameron’s Conservatives in last May’s election. Mr Corbyn, who this week opened a poll lead over the three other putative Labour leaders, would reduce to ashes what remains.