Robin Harding and Kana Inagaki:

Sakichi Toyoda, the founder of Toyota, once offered a ¥1m prize to the inventor of his dream: an electric battery that would free Japan forever from its dependence on imported oil. Toyoda imagined cars running on abundant hydroelectric power. All he needed was a battery to provide 100 horsepower for 36 hours, with a weight below 225kg and a volume of less than 280 litres.

That was in 1925. Almost a century later the prize remains unclaimed. Toyota’s engineers fondly refer to the elusive power source as a “Sakichi battery” and the very difficulty of making one has led them in pursuit of an alternative fuel to power its cars: hydrogen.

That pursuit is playing out in a small factory near the company’s headquarters in Toyota City, central Japan, where an elite team of workers are hand-building a vehicle that represents a huge gamble for the world’s second-largest motor manufacturer. The Mirai is either the future of the automobile or a technological trap about to swallow a prized swath of Japanese industry.