Japan was pioneering hybrid tech in the 2000s, but unlike Europe it had never seen diesel as appropriate for cars, so every hybrid used a petrol engine. It was France’s PSA Group that took the obvious – if technically challenging – step of combining the two: the Citroën Hypnos became the first car (albeit a concept one) to employ a diesel-electric powertrain, with 250bhp yet also 62.7mpg and CO2emissions below 120g/km. We saw market-leading potential, although the first production car, 2011’s Peugeot 3008 Hybrid4, was a commercial dud, and today only Mercedes-Benz perseveres.