They are words from Charles Dickens book "Great Expectations":
“The stones of which the strongest London buildings are made, are not more real, or more impossible to displace with your hands, than your presence and influence have been to me, there and everywhere, and will be. Estella, to the last hour of my life, you cannot choose but remain part of my character, part of the little good in me, part of the evil. But, in this separation I associate you only with the good, and I will faithfully hold you to that always, for you must have done me far more good than harm, let me feel now what sharp distress I may. O God bless you, God forgive you!”
He just says "strongest London buildings" and "in this seperation" but he has quoted the last line in some other performances.