THE UK’s newest fusion reactor has been fired up and is taking the country one step further towards generating electricity from the power of the stars.

Built at Milton Park by private company Tokamak Energy, the Tokamak ST40 reactor is the latest step in a five-stage plan to bring fusion power to the national grid by 2030.

The heart of the reactor - a super-hot cloud of electrically charged gas - is expected to reach temperatures of 100 million centigrade in 2018.

This is how hot it needs to be to trigger fusion.

Chief executive Dr David Kingham said: “Today is an important day for fusion energy development in the UK and the world.

“We are unveiling the first world-class controlled fusion device to have been designed, built and operated by a private venture.

“The ST40 is a machine that will show fusion temperatures are possible in cost-effective reactors.

“This will allow fusion power to be achieved in years, not decades.”

He said the project, now half way to the goal of fusion energy, still needed “significant investment”.

To date the company has raised £20 million from private contributors.

Dr Kingham added: “Our approach continues to be to break the journey down into a series of engineering challenges, raising additional investment on reaching each new milestone.”

Fusion power holds out the promise of almost unlimited supplies of clean energy.

It uses special forms of hydrogen as fuel, produces no greenhouse gases, and the only waste product is helium.

The plasma, which at 100m C is seven times hotter than the centre of the sun, has to be contained in a doughnut-shaped “magnetic bottle”.