The prospects for developing nuclear fusion as a feasible source of energy have significantly improved, say experts. The UK government has recently announced an investment of £200m to deliver electricity from a fusion reactor by 2040.  Private companies and governments have told the BBC they aim to have demonstration models working within five years. But huge hurdles remain, say critics.

With the price of wind and solar continuing to drop, experts say these existing renewables might offer a more economical and timely method of tackling climate change and generating energy than an unproven technology like fusion.

Nuclear fusion is an attempt to replicate the processes of the Sun on Earth. It differs significantly from nuclear fission, which has been our only way of getting electricity from atoms since the 1950s. Fission has proven to be hugely expensive. It generates large amounts of radioactive waste and raises serious concerns about safety and the proliferation of weapons.