In these days of PPI and subcontracting, the flow of public cash into private pockets is swift and relatively unchecked.

But what if the public sector’s mighty spending power could be used to force the private sector to act in the greater good?

That’s the principle behind Capital Letters, the collaboration between several of London’s town halls to buy up and share out housing stock instead of competing for it.

It’s good to see Haringey signing up to it: the less money councils spend buying homes (many of which, it has to be said, they were forced to sell decades ago), the further their housing budgets will go, which is desperately good news for those who were stuck in substandard accommodation like the Happy Vale Hotel.

But the idea councils should use their spending power to effect social change isn’t confined to housing. It’s the concept that drives living wage campaigns for public sector contractors; it is the point of the long-running Divest movement(s) to get public authorities to strip fossil fuel investments out of their pension funds. That cash can amount to millions of pounds just for a single council, and instructing schemes to invest it in sustainable energy and the green economy could make a big difference.

Anyone hanging around Camden Town Hall in December (despite the fact it was shut for refurbishment) might have seen messages from Divest Camden being projected onto the building. Camden said in response it took climate change seriously but believed in “robust engagement” with fossil fuel companies, which left Divest less than convinced.

Cuts have crippled local government, but councils still command an enormous amount of money. Camden is expected to put council tax up by 3.99 per cent in its budget this year. Now is the time to demand that it be spent securing our futures, not boiling the planet.