They are taking to the streets in Paris. They have secured a ban in Brussels. They have gone to court in Berlin. Taxi drivers across Europe are united against Uber – a Silicon Valley start-up, backed by Google and Goldman Sachs, whose app-based car service is being rolled out internationally.

The regulation of taxi services arouses emotions. My local French driver asked recently: “What do London cabbies do when they retire?” He explained that his colleagues rely on the onward sale of taxi licences to fund their pensions. In New York, the value of a taxi medallion now exceeds $1m. London, however, issues licences freely to anyone who passes “The Knowledge”, the demanding test of London’s geography required of drivers of the distinctive black cabs.

Some regulation of taxis is necessary. The nature of the service they provide means that many of its users are vulnerable. They are disabled, or women who need a safe trip home late at night, or foreign tourists who have no idea what is a reasonable fare from the airport to the city. Beware Budapest, where taxis are unregulated, and Oslo, where even the metered fare will max out your credit card.