The key to the FT-Bh’s high economy is energy-efficient on-board systems and an incredibly lightweight bodyshell, which uses a mix of high-tensile steel, aluminium and magnesium to bring the kerb weight down to 786kg, 25% less than a 1.0-litre Yaris. The knock-on effect was Toyota could use downsized chassis components and a smaller petrol engine, saving more weight and thermal energy losses.

As a result, the car can use a two-cylinder, 1.0-litre Atkinson cycle engine as a power source, contributing to a 90kg weight reduction for the powertrain alone.

The manufacturer said throttle responsiveness was high due to the low kerb weight, and even greater fuel economy could be reached with minimal modifications. Compressed natural gas would bring this down to 38g/km CO2, while a plug-in hybrid would emit 19g/km, Toyota added.