Called the RS5 Sportback, it’s a four-door version of the recently introduced RS5 coupé and so shares its 2.9-litre unit, co-developed with Porsche, that produces 443lb ft. It drives all four wheels via an eight-speed dual-clutch automatic gearbox.
The standard RS5, with its lighter two-door body, can accelerate from 0-62mph in 3.9sec. Expect the heavier Sportback to add a small margin to that figure, placing it closer to the four-door BMW M3, which hits the mark in 4.3sec.
Although this recently spotted development car is running S5 Sportback bodywork, its wider track, made clear by the fitment of wheel arch extensions, gives away its true identity as an RS5 Sportback test car.