By this time next year, they could be millionaires — or so say the makers of the Aptera 2e, the space-age American successor to the three-wheeled Reliant Regal driven by Derek “Del Boy” Trotter in Only Fools and Horses, an older British television sitcom.

Technology has moved on a long way since the Reliant made its debut in Britain amid the fuel crisis of 1973. For a start, the $25,000 Aptera 2e runs on batteries, not petrol, although the 4,000 or so customers who have already put down deposits will be offered a hybrid version.

Also, the third wheel is at the back of the vehicle, not the front, making the Aptera 2e look more like a UFO than a tricycle.

As if to emphasize its extraterrestrial looks, it comes only in a gleaming white.

“It might look crazy, but it’s crazy for a purpose,” said Marques McCammon, Aptera’s chief marketing officer, as he stood next to a row of half-built prototypes inside a vast production facility at Vista, California.

“By designing a car without a fourth wheel you basically cut the weight of the rear chassis in half, not to mention losing the rolling resistance of the tire. If this vehicle was given an official EPA rating, it would be 851mpg.”

Not bad, given that even a greener-than-green Toyota Prius hybrid can manage only 48mpg on a good day.

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