Mind-boggling magnets could unlock plentiful power

Dr Greg Brittles' eyes gleam with excitement when he explains the project he is working on.

"It's every engineer's dream really, to have a project that's technically challenging, which requires you to develop new technology and solutions to hard problems, but that are also simultaneously important for the world to have."

Since finishing his research at Oxford University five years ago, he has been working for Tokamak Energy, a UK start-up that has plans to build a fusion reactor.

Fusion is the reaction that powers the Sun and the stars. If that power could be harnessed on Earth it would provide a plentiful source of energy, from only a tiny amount of fuel and producing no carbon dioxide. What's not to love?

The principle is easy enough to understand. Take two hydrogen atoms, add enough heat and pressure and they will fuse together to form helium. During that process some of the hydrogen mass is transformed into heat, which you can use to make electricity.