The bastard of all crosswords

Every week I try to slog through the Listener Crossword. Printed on Saturday in the London Times, it is the most difficult crossword in the world. In about five years of attempting the thing, I have successfully solved it four times. The paper gives you three weeks to solve it, and the answers for the one from three weeks ago went live half an hour ago. This is the closest I've come to solving one in forever...

In order to solve any of the clues, you had to remove letters from the clues, it turns out the letters removed were blood groups in roughly the representative proportions (most of the time you were removing an O, or B, sometimes an A and in two cases an AB). This led to a quotation to solve on the left hand side which is the only part that escapes me. Oh Listener crossword, why do you mock me.