I've been thinking about this -- why she recognised me. Padfoot's right, I've fooled endless Ministry officials over the years, and plenty of people who had at least a passing acquaintance with Remus Lupin have looked at Junius Ponds without turning a hair.

Apparently what she recognised was my stance -- the way I walk, the way I slouch. It strikes me that as a fostered half-blood in Slytherin, she's probably learnt to be extremely observant of body language. I should have thought about this; it's nearly always the people at the bottom who are most closely observant of the people around them.