One of the big trends of the last 10 years has been the rise of coupe-cabrios.

The inspiration for the current crop was the Mercedes SLK, which presented it as a unique feature.

It set the Mark 1 SLK apart from all rivals.

Peugeot showed how the technology could be adapted for the mass market with the 206 CC, which proved popular with everyone except those who endured a mid-cycle roof failure.

Since then almost everyone has jumped on the bandwagon.

Sales of all lower medium cabrios grew steadily from 2000, but have fallen sharply so far this year.

#AM_ART_SPLIT# Of course, there are economic factors at work: when the economy turns down, sales of indulgence cars always fall faster than bread-and-butter models.

An Astra hatchback suddenly makes more sense than a £3,000 more expensive Astra Twin Top.

However, there is another factor at work that is a longer-term threat. A Focus CC, to take a typical example, is 240kg heavier than the equivalent Focus five-door hatchback and 190kg heavier than a Focus estate.

In fact, at 1,630kg, a Focus 2.0 TDCI CC is virtually the same weight as a Jaguar XK Convertible (1,635kg).

Why is that suddenly so important?

It’s because weight pushes up CO2, and all car companies need to reduce their average emissions. The Focus CC adds 10g/km- 12g/km of CO2 over the equivalent hatchback, depending on engine choice.

Given that most car companies need to reduce emissions by more than 20g/km of CO2 across their range, they can do without the penalty of a motorised steel roof.

In fact, the future of coupé cabrios may well depend on intense discussions currently under way in Brussels.

The EU intends to make CO2 limits variable according to the weight of a car – the heavier a car, the more CO2 it will be allowed to emit.

However, the limit will not be directly proportional to weight, as there would then be no incentive to make smaller vehicles.

So, for example, the allowance for a coupé cabrio might only be an extra 5g/km of CO2 rather than the full 10g/km of CO2.

Depending on the precise details of the legislation, the replacement for the current Focus CC might have a lot more in common with the old Puma than with the current model.

“EU legislation recreates affordable coupé market” – it could just happen.