The map above shows incidence of drug crime (darkening shades of green) against locations of nursery schools (red dots). As you can see, the Mayor need not worry about infant crackheads.

This and thousands of other comparisons can be made over on MapTube London, a new site from UCL's Centre for Advanced Spatial Analysis.

MapTube London allows you add your own maps of the capital, and compare data by overlaying different maps. The perfect way to spend those last few minutes before Friday night drinks.

But remember kids, correlation does not imply causation, as famously shown by the relationship between average global temperatures and number of pirates.