[In the dark, it's hard to assume someone would see him approaching, but he does indeed happen to be on the right side of Sorey, where a secret close by gives enough illumination that Lancelot doesn't realize and goes closer, tries to put a steadying hand on Sorey's shoulder from all that turning he's doing.
At least Queen Anne is beautiful is rather harmless compared to other things that could be next to them, right?]