We can’t help worrying about Gordon Murray’s T.25, since learning its likely dimensions earlier this month.

To recap, the T.25 is going to be quite tall, very narrow, and really short: about 240cm long and 130cm wide, in fact.

For those people who find abstract distances hard to comprehend, look at it this way: the T.25 will be about the same width as a GoinGreen G-Wiz. And 20cm shorter than a G-Wiz.

Now we’ve driven a G-Wiz, and it’s not exactly overflowing with leg and elbow room. Think economy airline. And don’t think about exuberant cornering unless your passengers don’t mind being elbowed in the ear.

A cramped interior is one thing, rubbish ride around town is another. In a city car, it’s a bit of a no-no.

Trouble is, the T.25 is just too small to cope well with that modern curse of the urban rat-run, the speed bump.

In the UK, lots of speed-bumps are of the “cushion” variety, which most drivers prefer to negotiate by straddling – driving so that the speed hump passes between the wheels. In the G-Wiz you can’t do that, and the T.25 will be the same. The UK Department for Transport recommends that cushion humps should be between 160 to 170cm wide. The T.25 is therefore 30cm too narrow to even think about straddling.

The other thing to think about is pitching up and down over full-width speed ramps. The shorter the wheelbase, the more pronounced the bucking-bronco motion as you try to smoothly pass over the sleeping policeman. And the T.25 is going to have a really short wheelbase.

When we drove the G-Wiz i, we found it easily capable of keeping up with urban traffic – except on all those inner city roads with traffic calming measures. Over the ramps, we had to slow to the pace of an arthritic snail so as not to flatten our heads on the roof lining.

The alternative is to fit suspension that’s ultra-soft in some circumstances and firm in others – using the kind of active springs and dampers that are found on expensive sports saloons and 4x4s. But given that Murray’s stated aim is to reduce the complexity of the T.25, somehow we doubt this will be on the cards.

So, er, it’ll be bouncing over the speed bumps, then.