I did see a boy fitting that description hanging around the LL/Upland Rd junction on Tuesday morning, and felt quite wary of him, having been the victim of a violent mugging a few years ago, carried out by a group of youths hanging around that bus stop on a Saturday evening. I immediately felt guilty for being suspicious - but now I know my instinct was probably correct. Sorry I can't add any more details though, as I was avoiding looking too closely in case I attracted his attention. I do feel so sorry for your son, and angry on his behalf - a 12-year-old ought to be able to cycle around an area like this independently and safely in daylight hours.