The difference between a concept car and a prototype is huge. It’s the difference between a piece of motor show eye candy and a viable proposition that has been made convincing enough to actually prove said concept.

This is the continuation of a thread I started recently, explaining the peculiarities, pressures and, often, disappointments that are associated with test drives in concept cars.

When you drive a concept car, you feel like a significant chunk of the story you write is about the art of the imagined. If this thing comes to be, just what might it be like? Such a car could supply perhaps 30-40% of that picture – or just 4%. But a prototype might get 90% of the way there.

There’s a greater sense of occasion to driving a prototype; manufacturers usually only allow it when they’re building up to introducing something really important. At this stage, a whole lot more has already been invested and more still is on the line. You might be driving one of only two or three very valuable examples of something currently in existence.

Sometimes, the full significance of what you’re doing isn’t apparent at the time. Back in the autumn of 2006, I went to Hethel, Norfolk, to ride in, rather than drive, a prototype of something called a Tesla.

The Roadster was, of course, a stretched Lotus Elise with so many laptop batteries where the four-cylinder engine would otherwise have been. I remember still how uncannily responsive and linear the performance felt – and that was while the car still had a two-speed automatic gearbox, so it tended to shift at about 60mph in a way that was noticeable enough to, well, lunch gearboxes, it would later turn out.