Since the end of his three-term New York City mayoralty in 2013, Michael Bloomberg hasn’t shied away from public attention. Presidential ambitions and global climate policy advocacy have kept him busy. But what is shaping up to be one of the most ambitious projects of the 82-year-old billionaire’s public life is not happening on the highly visible stages of national and international politics.

It is unfolding in the stereotypically humdrum halls of city government. Through Bloomberg Philanthropies – the vehicle for his personal and corporate giving – he has advanced an array of initiatives for city government leaders. The organisation is now providing funding and technical support to around 700 city governments across 150 countries – including Wellington City Council’s new digital community engagement tools .

In the process, Bloomberg has created for himself a historically unique and highly influential quasi-public position. As a kind of “world’s mayor”, he promotes a burnished version of his self-styled image while New York City mayor: eking out efficiency and effectiveness gains within city government through assiduous managerial control and better use of evidence. But Bloomberg’s inroads into global local government also raise important questions about the reliability of philanthropy over the long term – and its democratic legitimacy.

A ‘perfect match’? Bloomberg has described partnerships between philanthropists and government as a “perfect mat.