Hi! Sorry, I didn't see your comment before! A belated welcome to you!

I think, this time reading it, that he really did lose his memory, or at least some of it. There's a part where he's playing the lute for Christian and singing a lighthearted song about a frog and a well, and then suddenly:

The break was as violent as if death itself had struck. The four strings gasped, once, under his clenched fingers, and there was silence.

Alone with the hammering of her heart, with infinite patience, Christian waited.

"Memory's a strange thing." What aspect of the bold, ill-fated frog had opened the gates? Frogs--and wells. What lay at the bottom of a well? Cats; and kelpies; and curses; and cures for warts... and Truth, of course.

I think that was genuine. I don't think he would purposefully pretend to suddenly have a shocking flashback. For one thing, he likes to appear always in control of his mind and his emotions, never caught off guard. And for another thing, I don't think he would insult her by pretending. He might say "I don't remember anything" in an obvious but tactful manner that really means "I don't want to tell you," but I don't think he would go through such an elaborate pretense. And if he did, I think she would see right through it.

Plus, he was speaking the name "Jonathan Crouch" in his sleep, and even that is a sign of suffering Lymond. Healthy Happy Lymond is SO much in control of himself that I don't think he would talk in his sleep. He's had a pretty nasty knock on the head, and he's pretty messed up. And he's rather shaken when she mentions the name to him.