One of the most difficult aspects of designing an electric or hybrid car is packaging the batteries. A plastic fuel tank can be blow-moulded into amazing shapes and squeezed into the space under the rear seat.

Batteries, however, are big and square and demand lots of space.

At the Detroit show, I noticed that back-up battery for VW’s hybrid concept coupe swallowed up a considerable chunk of the otherwise giant boot.

The Mini E, of course, loses its rear seats in an attempt to squeeze in enough battery power to propel the car a claimed 120 miles.