France’s richest man, Bernard Arnault, is shifting his fortune to Belgium. Gérard Depardieu, the country’s greatest actor (figuratively and literally) is moving to Russia. And, if rumours are to be believed, Nicolas Sarkozy is planning a new career in London.

That’s the problem with very high taxes – they don’t redistribute wealth; they redistribute people. It’s easy to say, as François Hollande did during the 2012 French presidential campaign, that the rich should hand over 75% of their income. But the rich don’t sit around waiting to be taxed. Friendlier jurisdictions are just a Gulfstream flight away, and many financiers can open their businesses abroad simply by opening their laptops. The result of a hike in tax rates is thus often a fall in tax revenue – which means, of course, that the rest of us end up paying more to cover the share of the departed plutocrats.

In Davos, David Cameron has called for international action against what he calls legal but unethical tax avoidance. The trouble is that there will always be countries seeking to attract tax exiles.