The Times today reported that Boris Johnson has asked David Cameron for extra powers should the Conservatives win the next election. These would include responsibility for housing, rail transport, traffic on the Thames and emergency-planning functions. His request is concurrent with George Osborne’s insistence that under a Conservative government many powers would be devolved to local governments, with various quangos disbanded in the interests of greater efficiency.

Aside from the question of whether it wants to transfer greater influence to Johnson specifically (the man who informed the electorate that ‘voting Tory will cause your wife to have bigger breasts and increase your chances of owning a BMW M3’, has had to apologise under strained circumstances to both Liverpool and Papua New Guinea, and stunned audiences at the Beijing Olympics with an animated analysis of ‘Wiff Waff’) the electorate should consider what it wants the role of its mayor to be.

At over 7.5 million Greater London is a huge entity. On the face of it there seems to be a great deal of logic behind extending the powers of its elected assembly to deal with its own affairs. Indeed, to the extent that the extension of the mayor’s powers facilitates ‘economic development and wealth creation, social development, and the improvement of the environment’ they should be endorsed. It seems, for instance, that giving the mayor a say on rail franchising contracts - Johnson points out that over 70% of train journeys in the country begin or end in the capital – would promote these ends.

However, the forced resignation of Sir Ian Blair and Kit Malthouse’s recent assertion that Johnson’s administration has its ‘hands on the tiller of the met’ indicate that, determinated to beef up his mayoral powers, Johnson is threatening the autonomy of the police. The mayor's influence must not be extended too far.