Well, some people tend to take what characters say literally, that is, they believe that "I love you" means "I love you", although saying it can also be a means to make other person do or give something. (And of course also "love" can mean many things.)
As you so splendidly show, we must never forget that Philip is a spy and acts like one. His motives are best seen in the result he achieves. That's not mean that he doesn't care for Martha, in a way he does, but also this caring is almost to the end a means to make her do what he wants.