Both big political parties in the UK intend to decarbonize the electricity grid. The Tories say they will do it by 2035; Labour says it will by 2030. When they made these promises, it probably felt like it could be pretty easy. Bit of wind here, bit of solar there, chuck in some hydrogen, a few advances in battery storage, a new nuclear plant for a bit of back up — and, hello, carbon-free grid.

It turns out this isn’t remotely easy.