A fresh report out of the United Kindgom suggests Mercedes-Benz’s high-performance arm is hard at work developing a Mercedes-AMG GT73 4Matic+ flagship, complete with plug-in hybrid technology and around 600 kW.

Autocar published spy photographs of a GT 4-Door Coupé test mule, showing what the publication describes as a “complex electrical system” under the bonnet. The report also claims the prototype drove away silently (i.e. on electric power alone).

According to the report, the production model is set to hit the market in 2020, slotting in above the GT63 S (which makes 470 kW and 900 N.m).

Of course, the brand’s Affalterbach-based performance arm previewed its current GT 4-Door Coupé range with the GT Concept back in 2017. And that show car featured the firm’s twin-turbo 4,0-litre V8 mated to an electric motor, resulting in a total system output of 600 kW (and a claimed 0-100 km/h time of less than 3,0 seconds).

As Autocar pointed out, the “73” badge was last used on the SL73 AMG, which drew its urge from a 7,3-litre V12 engine. Earlier reports suggested the German automaker had also filed trademark applications for the G73, S73 and GLS73 monikers.