A huge proportion of people who tow 2 tonnes+ are doing so illegally - unwittingly, perhaps, but still illegally. I suspect the percentage of illegality grows considerably with the weight of the trailer, too.

This has obvious legal and safety implications. And of course manufacturers are in an 'arms race' where 3.5-tonne tow capacity is not just the 'gold standard' - they know they're not selling as many cars as they could if they don't offer that.

Compliance is not as straightforward as it sounds - so here's how you crunch the numbers to stay 'roadside weigh station ready'.