Their recent episode on sustainable energy was very interesting, but fell into the trap that numbers can often set. The key interview was with Professor David Mackay, who has spent a long time doing very detailed calculations on what energy we could realistically harvest from which sources, and what sort of things we are actually using our energy on.

Asked whether it was worth switching off our mobile phone chargers when not in use, as we are often reminded to do, he scoffed that it was almost entirely pointless and we really shouldn’t bother – the energy used was about the same as driving a car 60m, and measured nothing compared to so many other things.

I think this misses the point, and raises one very important principle that a simplistic rational look at the numbers fails to see: turning off your charger won’t save the planet, but it’s a discipline that reminds us, like a mantra, to think about the bigger decisions we are making with our energy use.

This is the principle of ‘living symbolically’ that I talk about in the forthcoming book: taking actions that are not necessarily effective in themselves, but act as symbols pointing us or others to greater actions that may have a much larger impact.

There’s been quite a lot of environmental pessimism around at the moment – we’re buggered anyway, so why bother changing my lifestyle? – so I feel that it’s more important than ever to take actions, even if they are symbolic, in the hope that collectively these will show those in power that there is real political will to make things happen.

Head over to generous.org.uk to sign up for some actions yourself.