This week Boris Johnson, mayor of London, has been banging his drum in New York. He is not, however, promoting his ideas about Europe, the Conservative party or Winston Churchill, the subject of his latest book.

Instead, Mr Johnson is doing the cyber version of taking coals to Newcastle: telling American tech entrepreneurs that London is a cool place to work and invest. Never mind Silicon Valley or New York’s Dumbo (Down Under the Manhattan Bridge Overpass); US entrepreneurs and investors should head to Shoreditch and Bournemouth. Or so Mr Johnson’s sales pitch goes.

It is something of a quixotic mission but is nevertheless notable for at least two reasons. First, it offers a useful reminder of how fashions in the political economy can change. A decade or so ago, when British trade missions tried to “sell” London to New York, they talked more about banks than computer bytes. Back then, people such as Ed Balls, when he was a Treasury minister, were keen to extol London’s light touch, “principles-based” regulation as a competitive advantage versus New York.