Though he'd corrected if to when a moment ago, he has no actual way of knowing whether Alex will actually come again. It might have been the last time they'd ever seen him, that day with all the visitors -- Galahad had a sense of that even then, and it's why he'd wanted so much to draw Alex while he could. It's why he did so many portraits, to try and capture some part of Alex for Magnus to keep.

He holds onto Magnus, rubbing his fingers through Magnus' hair -- it's getting long again. He doesn't know how to answer. He doesn't want to lie. The thought of never seeing Percival again makes him feel as small and tremulous as Magnus' voice is, but it feels wrong to promise Magnus something that might not happen.