If it's pretty normal then why is no one else seen wearing one in the CCTV footage or descriptions of who was around the area at that time.
I live in central London on a high street and most people in town at that time are people coming out of bars, clubs not dressed in hoodies. Yeah it's the kind of thing a teenager would wear but what's a teenager doing on the street at that hour, I'm pretty sure it's safe to say up to no good in some shape or form.
I have to say, if I was to enter a secluded area for a pee and a person was in there with dark clothing and a hood up the last thing I'd want to do is get my "lad" out and have a pee.. but that's just me clearly