That expanse of emptiness up there is how the tube map looks when it's sorted by affordability of housing, with the data populated by housing charity Shelter showing that the only winners in London's housing market are people who bought homes in the 1980s and the rail companies that ferry workers in from ever increasing distances away.
Shelter says: "Of the 270 stations on London’s Underground network only 15 are in areas where private renting can be considered genuinely affordable. With more than one in four people in London now private renting, this can't go on. And it's why we're asking Londoners to join us in ensuring the new Mayor commits to fixing renting in the city," to which end it's put up a petition, as if we live in a democracy.
Here's the full thing. It's still pretty bleak, unless you're lucky enough to have a rental portfolio in the Golders Green area:
For the purposes of the exercise, Shelter defines affordable as being at a cost of "less than 35 per cent of the combined take home pay of a two-wage household" with the difficult to afford bracket being between 35 and 50 per cent of the same household's pay, and both assuming an average salary is being earned. [Shelter]