I'm pretty sure it's not the accent he grew up with as I worked in Teddington for a while and nobody spoke like that there. It sounds a bit East End but not quite right, the 't' sounds are wrong for instance (I lived in East London for about 10 years). Is it maybe a North London accent? Is it something he's made up himself to get hard man roles (if it is he's been very consistent with it, I've never heard him use any other accent)?
I have fancied him for ages, it's something to do with the combination of a very deep, gravelly voice and the occasional echo of his father (my childhood Doctor Who).