While it would be a mistake to shut them off, or to immediately abandon gas usage while renewable capacity is built up, ultimately power can be made and stored cheaply enough using wind and solar, says Harald Överholm, former solar markets adviser to the Swedish government and founder of Alight, which builds and operates solar farms.

He says the answer is to “over-build” renewables such as wind and solar and then use them to generate hydrogen on windy and sunny days to act as a power bank for when demand outstrips supply. 

Hydrogen made from water using electricity can then be burned, producing water again.

“The long game of transition is 100pc solar, wind and electrification. This is a valid plan. This really works,” he says. It will take time and involve declining costs for energy generation and storage, however.

But for Juan Matthews, a visiting professor at the University of Manchester at the Dalton Nuclear Institute, nuclear power is critical to keeping the lights on, even as more and more cheap wind and solar power is delivered.

He says that the volatility of wind and solar power means that a few days’ worth of electricity storage would be needed, something that can only be delivered at great expense today.

“I do support renewables, but renewables have a big problem,” Matthews says. “What we need is a balanced selection of energy generation sources that have a low impact on the environment with low carbon emissions, and nuclear is one of those.”

While excess energy from renewables can be stored, for instance by powering pumps to send water to reservoirs at height, to be harnessed as hydroelectric power when needed, this is an expensive process.

And for making hydrogen, using expensive electrolysers only part of the time to build up reserves is a waste and requires similarly expensive storage.

He says nuclear is a better bet for making hydrogen too, because the electrolysers needed to strip water molecules of their hydrogen atoms need to be run continuously to be at their most efficient, and nuclear can provide power day and night.

Supporters of pure renewables point out that the cost of electrolysers is likely to come down, together with lots of other clean energy technology, although many use rare metals such as iridium, which has doubled in price in the past two years.

There are also opportunities for storing power in the nation’s growing fleet of electric cars and banks of batteries that continue to get cheaper.

But nuclear has another advantage in that the energy starts off as heat, allowing for more options with storage when a power bank is needed, Matthews says. Nuclear power stations can be built with extra generation capacity to make use of extra heat stored in rocks or as molten salt, making up for gaps in renewable production.

The heat can also be used in new processes to make hydrogen from water that do not require expensive catalysts, further cutting costs.

Finally, he says, Rolls-Royce’s technology can be made largely in Britain. The mini reactor project has attracted £490m of capital – a sign investors are confident in its necessity, says Samson, and a way out of Russian gas.

“The UK is responding to this crisis with a technology solution. This is an exportable product that can help other countries in their energy independence and security and supply as the landscape changes for Russian fossil fuels and gas.”