While at first, and even second glance, the Bentley Continental GT in the photos looks pretty unremarkable. In every sense, it's just a normal example of the latest Continental GT . On that third glance, though, you'll notice one extremely subtle detail that's off: it has a second fuel-filler door. That leads us to believe that Bentley has a plug-in hybrid version of the Continental GT on the way, and it's almost ready for production.And when we say this is a subtle change, we mean it. Unlike many PHEVs that have both filler doors on one side, this Bentley has one door per side. So from the side, there's nothing to tip you off to the strange addition. You can only notice the extra door from the rear, which shows both doors on the tops of the rear fenders. Either that, or you would have to know that the regular Continental GT's gasoline fuel door is on the right side of the car, not the left.As for what sort of hybrid powertrain is in this Continental GT, we would suspect it's the same as that in the Bentayga Hybrid revealed at the Geneva Motor Show earlier this year. It uses a turbocharged 3.0-liter V6 with an electric motor. Power and fuel economy haven't been announced for that powertrain, but Bentley says it is capable of driving the big SUV for 31 miles on a charge on the European cycle. We would expect the lighter, more aerodynamic Continental GT could probably eke out a few more mpg with the same setup.Considering that this test car was completely undisguised, and that it will likely use an existing powertrain, we expect this hybrid Bentley to be officially revealed soon. An announcement early next year with sales coming later that year seems plausible.