It's a scary thought, isn't it, Figgy?
It's either that, or just a confluence of various circumstances that led to Morgan becoming vulnerable to an unstable person. Though I -do- think DJK stalked Morgan that particular night.
Who knows, maybe DJK had dreamed up a real chance for romance in his head.. was feeling particularly lonely/needy that day... and saw his chance to try it on with a guy he'd admired from afar (or not so afar, seeing as their haunts overlapped) for some time.
Then Morgan squished all his hopes and dreams...
I really hope we get to know the details of this crime. Not just for satisfying curiosity (though it's a factor!) but also just for knowledge of how DJK was set off into murder..
ETA: if he WAS stalking Morgan for a long time, it would not have been hard at all - easy access/visibility to Morgan's st via Cheal Lane from the rear of the cooking school.. hanging around in food shops that all look directly into the pub where Morgan was a "fixture"... etc.. It is very possible, in my mind.