Sadiq Khan won the contest to be Mayor of London two years ago promising to make tackling crime his top priority. After two more murders in the capital, bringing the total since January to 39 – more than in New York City – it is a pledge that looks increasingly hollow.

More than that, Mr Khan seems to be frozen into inactivity. The city that he leads is facing a violent crime crisis and yet the mayor is doing nothing beyond issuing statements expressing his concern and blaming others for what is happening.

Mr Khan is hamstrung by the countervailing strategies that nowadays afflict all politicians for whom virtue signalling is more important than dealing with the realities before them.

The mayor...