Majarvis
Not true. The Bentley was a completely different design, basing its concept on the knowledge gained from the R8, but it had nothing to do with the R8C. The R8R and R8C were just a way for Audi to see which road to go down, closed or open cockpit, and when they decided that the open-cockpit was the beneficial route, they stuck with that.
Well, how can I explain this to you...
In 1998, Audi started working with Dallara and the Joest team in the Audi R8 (at that time, they even didn't know if they would build a car with an atmo engine or a turbo one).
Then, after designing the first version of the R8R, they decided also to comission RJN in Norfolk (were Tom's Toyota was based before) for the creation of a closed coupe (the R8C) because they didn't know which was the best.
However, even if they raced at LeMans in what became the evo3 version of the R8R (unofficial name) and the R8C, the Audis were not that fast (while the R8C was even slower and less reliable). From this on, Audi concentrated in the open top route.
In spite of this, RJN continued developing the R8C, firstly by giving it a GT-One-"esque" look in 2000 (the car ran, it seems, with a Cosworth atmo engine) and then designing the first variation of the Bentley EXP Speed 8 (which, ofcourse, was a lot more develloped than the R8C), which used a 4.0 litre Audi engine (similar to the 3.6l in the Audi R8).
So, what I meant was that, while the R8R develloped into the R8, the R8C was then develloped to the Bentley, thought both of them had a lot more R&D incorporated to it, which meant the very different (and better) aero and engineering.