This is a silly, and potentialy dangerous political gesture. However brilliant Turing was, he broke the law and was convicted. A royal pardon can not undo the punishment he suffered. And it is a dangerous track upon which to embark: many regimes have systematically rewritten the history books according to their own ideologies. How soon before the book burning begins here?
I have to be honest, as a queer black short sighted woman... what does this actually mean? If it it meant anything, then I'd hope all the other homosexuals who received similar treatment from the justice system at that time also received Royal pardons, unless we're saving pardons only for mathematically gifted homosexuals? It's a wonderful thing that the injustice of previous eras is highlighted, but surely not to make us in the present day seem more righteous. Rather, shouldn't it serve to give us the courage to look at ourselves in the light of history as well? I'm no conspiracy theorist, but those of an embarrassment to the State (or the Church) are still being shabbily treated, but now there are different sticks to beat them with.