Nick Hawker is standing inches away from a gun that can fire bullets at 33,500mph. “Let’s just say, it wouldn’t end well if somebody got hit,” he laughs. This is the fastest railgun in Europe; a 40ft (12 metre) pulsed-power machine capable of discharging up to 200,000 volts – the equivalent of 500 simultaneous lightning strikes. The device is in the secretive laboratory of First Light Fusion, in a bucolic corner of Oxfordshire. This place, claims the 34-year-old scientist, is one of the best hopes the planet has of creating limitless clean energy through nuclear fusion. Hawker is not quite ready to change the world just yet. “Fusion is definitely, definitely coming. This is the decade... but like everything in energy, it takes time.”...