We’ve seen some extreme versions of the SLS AMG, notably the 700bhp Brabus 700 Biturbo and the 636bhp Hamann Hawk. But the one we’ve been feverishly waiting for was Merc’s own Black Series SLS. Now we’ve got proof that Stuttgart is seriously pursuing the project as our spy has finally spotted the hardcore Gullwing being tested in Germany. The matte black mule reveals broader fenders, a wider track front and rear, a front bumper with larger air intakes and new side skirts. The wheels and tyres are also bigger than the stock car’s. Although we don’t expect the Black Series to match the Brabus’s ridiculous output, Mercedes should squeeze out at least 650 horses from the 6.2-litre V8. The seven-speed dual-clutch tranny as well as the suspension will also be beefed up to handle the extra grunt.