I had thought the apogee would be the V10 Audi RS6 Avant, in which they put all but a Lamborghini engine in the front of a big estate car. How very amusing but how very ludicrous, I thought, as we stuck it on the scales at MIRA shortly before doing a 4.4sec 0-60mph time. When fuelled, it tipped the scales at 2145kg.

That afternoon, some time in 2008, it went and posted the fastest time we had yet recorded on MIRA’s perma-hosed wet handling circuit. It cut through standing water to lap in 1min 6.1sec – 2sec faster than the Audi R8 of the time and 3sec faster than the McLaren 720S (although surface changes have thrown later figures a little out of whack).

But that number: 2145kg. Sheesh. We won’t see the likes of this again, I reckoned, as we sat in the MIRA canteen (whose puddings are a good way to contribute to one’s own girth).

A while later, I attended an event run by the Niche Vehicle Network, a very cool association of more than 900 specialist companies that shares information, aims to get funding and exists to promote niche vehicle manufacturing and engineering.

There, a materials engineer from a major car company outlined how light cars would have to become if, conventionally powered, they were to meet incoming environmental restraints. Composites would have to be cheaper to make it possible, it was reckoned, because a city car would have to weigh less than 600kg and a family car not a great deal more.

Difficult to achieve but exciting if it could be done. Because what could be cooler than a whole load of light cars arriving? Half-tonne city cars would be compact and therefore impossibly agile. Making sports cars out of them would be a doddle. What a laugh.

Naturally, then, I’ve spent much of the past week in a family-sized Audi that has a kerb weight of 2520kg.

Going by the measured weight of an E-tron variant we road tested last year, you can call this Sportback 2600kg by the time you pop on some options and ease it onto a set of scales.

It passes environmental inspection by dint of emitting no CO2 and no gases to harm air quality. At least, not at the tailpipe. And for the E-tron’s kerb weight you can thank, in part, the 95kWh battery under its floor that weighs the best part of 715kg.

I enjoyed the E-tron. It’s one of the world’s more relaxing ways to get around. But when driving it, I could never quite escape the feeling that I would rather have been at the wheel of something a fifth of its weight.