The upcoming Mercedes-AMG GT 73 has been previewed in prototype form in a video clip, giving us our first glimpse of the most powerful 4-door GT car yet launched in motion.

The GT 73 is reportedly based on the 2017 AMG GT Concept and will supplant the GT 63 S as the range-topping model in the lineup. The new video also confirms expectations that the model will be a hybrid.

Following the example of the concept, the new variant looks set to receive a twin-turbocharged 4.0-litre V8 petrol engine with an electric motor on the front axle.

A whirring sound emitted by the car as it speeds away from the camera seemingly confirms its powertrain, suggesting it will arrive as a plug-in hybrid.

Between them, the V8 and electric motors will allegedly produce north of 800bhp - considerably more than the GT 63 S’s 630bhp, and that of the 671bhp Porsche Panamera Turbo S E-Hybrid.

Power is expected to be transmitted to all four wheels via the same nine-speed automatic gearbox as the GT 63 S, while accelerating from 0-62mph should take less than 3.0 seconds.

The new model is also expected to be the most economical - on paper at least - in the lineup, with an expected electric-only range of about 31 miles.

While Mercedes has confirmed that the GT 73 will be launched in 2020, the exact date has yet to be specified. The Geneva International Motor Show in March, however, would be a natural time for the debut.

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