Question Author
ichkeria - //There is a lot more to acting than being able to adopt different persona. //
There is, but it is still a fundamental principle of the craft.
Acting - by definition, means playing a part, and if you are playing yourself, you are not playing a part.
So at one extreme you have Nesbitt, Caine and Connery, and at the other you have people like Johnny Depp and Leonardo Dicaprio, and let's never underestimate Paul Whithouse - whom Johnny Depp rates as one of the best character actors in the world - and he would know.