The future range-topping car, first confirmed back in 2016 by AMG boss Tobias Moers, is now under development and is likely to receive AMG's turbocharged 4.0-litre V8 engine in a state of tune that offers at least 638hp. This is the figure offered by the current most powerful AMG model with that unit – the recently revealed GT 4-door Coupé – which, in turn, dwarfs the peak output offered by the carmaker's current GT champion, the 585hp GT R. The Black Series would also go head-to-head with one of the category's most radical supercars – the 700hp Porsche 911 GT2 RS.

The GT Black Series' extra power will be accompanied by a more focused chassis and aerodynamic set-up. A development car dressed in GT R clothing was recently spotted at the Nürburgring. It's believed to be part of the Black Series test programme and offers some clues as to what's to come.

The test GT wears more extreme bodywork that borrows parts from AMG's GT4 racing car, with a fixed rear wing and exhaust exits now farther apart in the diffuser than their normal central position. These changes will enhance downforce at the car's rear. Similar pressure-adjusting features will undoubtedly be added to the front to ensure the car has a balance which is fit for track work. Larger brakes and wider wheels are also expected.

The test car also seems to have a polycarbonate rear window, which will save weight. Its use suggests that several other mass-trimming parts will be fitted to the Black Series, while non-essential parts could be ditched. Inside the photographed development car is a pair of sports seats and a roll cage. Although the latter is available as an option on the GT R, it’s likely to be standard on the Black Series. Such a setup ensures that the GT Black Series tips the scales at around 1,600kg – making it 30kg lighter than the GT R. Add the car's light weight to the V8's extra potency and the Black Series looks set to become AMG's fastest production model this side of its highly exclusive Project One hypercar.

The 2020 arrival of the GT Black Series will mark a return for AMG's most extreme moniker after a seven-year hiatus. The last Black Series model was based on the SLS and entered production in 2013.