Scientists with their heads in the clouds

Here we go again,

. Engineers at Liverpool University are planning for aerial highways to be designated, enabling well-heeled commuters to flit here and there in cars that transform into helicopters. At this stage, anyone over 60 has a deep sense of deja-vu.

We have been told ever since the 1950s that the age of car/plane hybrids is at hand and, before long, everyone will have a pair of wings or rotor blades stored in the garage to convert the family saloon into an aeroplane.

It hasn't happened for one very good engineering reason. Cars are cars, planes are planes and, for that matter, boats are boats. Whenever someone designs one that turns into the other, you end up with a rubbish car that transforms into a useless plane or a hopeless saloon that turns into a frighteningly unseaworthy boat.

And where are the chic, image-conscious millionaires who are prepared to buy a pokey little helicopter that converts into a car resembling the old three-wheeler invalid carriage? When people talk seriously about such things it is probably because they spent too much time as a child watching the puppet series Supercar.