Firstly, it's a father and son team. The father is a Professor of Linguistics, while the son is an actor.
David Crystal has done much research on this topic, and if you're interesting in reading about this:
http://www.davidcrystal.com/books-and-articles/shakespeare
https://www.amazon.com/Pronouncing-Shakespeare-Experiment-David-Crystal/dp/0521852137
https://www.youtube.com/watch?v=5lOFAzt8fMg
While Ben Crystal, the actor, is very aware of his own accent and the many accents which he works in as an actor. One big requirement of actors in the UK, is that they're able to do accents very well.