THE most powerful Mercedes-Benz SLK of all time, the 55 AMG model, will cost £54,950 when it hits the road later this year.

Low slung and stylish, the 55 represents the high-performance pinnacle of the SLK range and is powered by a new direct-injection version of AMG's 5.5-litre V8 engine.

It develops 421bhp and a hefty 540Nm of torque, meaning 0-62mph acceleration takes a fleeting 4.6 seconds en route to a limited top speed of 155mph.

Yet fuel economy and CO emissions have been reduced by 30 per cent, through the introduction of AMG's Cylinder Management System, similar to that on Mercedes-Benz Formula 1 engines.

This shuts off two cylinders on each bank of the V8 when the car is running on light throttle loads, and an ECO stop/start system is also fitted so that the SLK 55 AMG uses no fuel and emits no CO2 when stationary in traffic. Combined fuel economy is 33.6mpg, with CO emissions of 195g/km.

The engine is paired with a seven-speed AMG Speedshift 7G-Tronic PLUS automatic transmission featuring Controlled Efficiency, Sport and Manual modes.

Sports suspension featuring Torque Vectoring Brake and the AMG Direct-Steer is fitted as standard, so there's serious grip and agility for performance-oriented drivers along with long-distance ride comfort.

Taking its design cues from the SLS supercar, the 55AMG comes with AMG body styling with exclusive front and rear aprons and side skirts, high-performance brakes, sports suspension, leather upholstery and 18-inch five-spoke alloys.

Advanced safety features include Pre-safe, Neck-pro, Attention Assist and Headlamp Assist while there's also the Mercedes-Benz Intelligent Light System, COMAND Online with Media Interface and a DAB digital radio.

Options are headed by the AMG Performance Package of revised suspension and brakes with a rear differential lock (£4,105) and the Driver's Package, which raises the limited top speed and includes attendance at an AMG ‘Power and Passion' driver event (£2,755).