Researchers at the Joint European Torus (JET), a fusion experiment in Oxfordshire, generated 59 megajoules of heat – equivalent to about 14kg of TNT – during a five-second burst of fusion, more than doubling the previous record of 21.7 megajoules set in 1997 by the same facility.

The feat announced on Wednesday follows more than two decades of tests and refinements at the Culham Centre for Fusion Energy and has been hailed as a “major milestone” on the road to fusion becoming a viable and sustainable low-carbon energy source.

“These landmark results have taken us a huge step closer to conquering one of the biggest scientific and engineering challenges of them all,” said Prof Ian Chapman, the chief executive of the UK Atomic Energy Authority. “It’s clear we must make significant changes to address the effects of climate change, and fusion offers so much potential.”