Boris Johnson, the Conservative mayor of London, hailed a “new era of co-operation” between London and New York after meeting Michael Bloomberg, his transatlantic counterpart, at City Hall on Friday.

The two mayors announced an “innovation exchange programme” to swap personnel, as well as ideas in areas such as transport and policing. But the high-profile meeting was more of a publicity coup for the Tories, in their first week of running the capital, than a substantive forum.