It’s nearly a century since it was discovered that the sun and other stars are powered by nuclear fusion. It’s when hydrogen atoms merge to form helium, and release huge amounts of energy.

Since then, scientists have dreamed of reproducing the process here on Earth, with one Nobel Laureate calling it “the sun in a box”.

It holds the promise of virtually limitless energy, with few emissions and waste. But recreating the conditions where fusion can take place are a vast engineering challenge. So how close are we to having a working reactor powered by fusion? And will the process solve all our energy problems?

Presenter: Tanya Beckett Producer: Louise Clarke-Rowbotham