BRITAIN'S most popular new sports car has gone hard-core.

On March 4 the first batch of 500 2017 Mazda MX-5 Retractable Fastback models with an "origami-style" aluminium powered folding roof will be driving out of showrooms and into spring.

After the runaway success of the MX-5 convertible, Mazda says it believes the RF will take about 75 per cent of 3,500 sales this year.

This latest fourth generation of the two-seater which has found favour with 120,000 British enthusiasts since 1990 has the newest 131ps 1.5 from May, or launch model's 160ps 2.0-litre engine with six speed manual gearbox or for the first time in the new series, a six-speed automatic.

Power is up and so is economy and the larger engine models have revised steering, brakes and suspension to cope with the additional power over the smaller unit.

The SE-L Nav and Sport Nav trim levels are familiar although the first launch batch of 500 models come with distinctive alloy wheels, Recaro seats and upholstery, standard Safety Pack, black roof section, door mirrors and boot-lid spoiler with red or grey metallic paint. Prices generally are about £2,000 more for RF versions of the two-seater range.

Despite the fitting of the powered roof, the engineers managed to keep the luggage space for a couple of weekend soft-bags or shopping while the folded hardtop sits in its own compartment between the cabin and bootspace.

Jeremy Thomson, Mazda UK managing director, said the MX5 is a crucial car for the company, with 12 per cent of sales in Britain and globally a million are on roads.

In a few weeks, Mazda anticipates announcing 1.55 million sales of all its models since March 2016 a rise of 50,000 on previous 12 months.

"UK sales went up 10% in 12 months compared to 7% in Europe and that was remarkable given the challenges of currency exchanges and headwinds of the Brexit negotiations," he said.

The previous third generation of the car included a hardtop and as it was run-out the soft-top was being overtaken by the metal topped version, so the newcomer arrives on the crest of a customer wave.

Now deliberately styled to resemble a coupe, rather than an open topped car with a roof just slid on top, the b-pillars are made from composite materials to give sharp angles and edges to them and it looks a different car to its soft-top convertible stablemate.

Mazda has made coupes since 1968 and the Japan-market only Cosmo, but some enthusiasts will remember the NX-7 which was the basis for the Ford Probe, the MX-3 with unusual V6 1.8-litre engine and of course the groundbreaking RX-7 rotary coupe which won numerous championships and endurance events.

Ironically, the new MX-5 is the basis for the Fiat 124 and Abarth Spider models, but they use their own powertrains.

For the new 2017 MX-5 range, Mazda expect 75 per cent will be RF versions, and 60 per cent will be the 2.0 litre derivatives and early orders suggest 15 per cent will be supplied with the automatic transmission and 29% will be the higher Sport Nav trim.

The launch series will be £28,995 with the extra equipment and paint details while the remaining five-model range will then run from £22,195 to £27,095.

In the metal, the "targa-style" top to the RF version sets it apart from its stablemate while the sweeping rear pillars give it a true coupe profile when the roof is closed.

We tried out both the 2.0-litre and 1.5-litre versions with six-speed manual gearboxes. Of the cars we drove, one displayed a rattling roof trim but otherwise they were refined and quiet with very agreeable exhaust notes.

The 2.0-litre was more of a grand tourer and because it did not have to work so hard it gave us 36.3mpg while the edgier 1.5, which felt lighter, returned 35mpg.

Only in very hilly countryside were we aware of the reduced power in the 1.5, which necessitated downchanges. It was eager and responsive while in the 2.0-litre there was simply more underfoot and the power band had a better spread.

The excellent driving position remains for anyone up to 6ft, the boot is small but deep and wide and compensates for the lack of oddments space. Visibility is excellent and when the roof is open there is little wind ruffling around the neck while the heater does a really good job on a cold day.

The Mazda MX-5 has always and rightly been a success, and the RF simply moves it on and gives you an open or shut case for buying.