Rape by Deception / Mistake?

The Daily Telegraph reports on a case that would usually just be a strange hypo in criminal law class. When reading the case, ask yourself what the result would be or should be either (1) if the defendant was telling the truth when he says that he was just mistaken, (2) if the defendant was lying, and actually knew whose room he was going into, and (3) if the defendant was mistaken at first, but at some point realized his error but for one or another reason didn't stop.