The model, which is described as "the ultimate expression of British automotive luxury," and "the most sophisticated open-top car ever created by Bentley," is powered by the same 6.75-litre twin-turbocharged V8 engine as the Mulsanne and Mulsanne Speed.
Bentley quotes official power output figures of 530bhp and 811lb ft - the same as the Mulsanne Speed. In that car, the engine is capable of delivering a 0-62mph time of 4.9 seconds.
Company officials have told Autocar the car will make production, and will retain its Grand Convertible name. However, customers willl be able to give their own 'official' name to each model, too.
It is understood that the model has taken five years to bring to production - largely because so much of Bentley's resources have been put into developing its SUV.
A coupé version of the Grand Convertible could also come to market, though has yet to be given the green light by Bentley officials. Such a model would work well in Europe, but demand in Bentley's two biggest markets - the US and China - would be small compared to demand for the open-top car.
Previewed as far back as 2012, the Grand Convertible has previously been rumoured to cost around £275,000.
Virtual concepts for the coupé have already been created, with officials saying it looks "absolutely stunning."