The other thing Merlin has never really let Arthur know before the last episode is exactly how much he loves him (in whatever sense) and you really see that here.

Oh yes. It was absolutely shattering.

Hooray for a Doctor Who crossover! However, now I'm curious. The regenerations post Seven would be aware of their own potential Merlin-ness, wouldn't they? And Ten post Midnight as well as Eleven would at the very least experience a sense of Deja Vu when looking at Merlin. (Because of Colin Morgan playing Jethro.) Or will the crossover be with pre Seven Doctors?