I think he kept SB for a period of time before killing her. I'm just wondering if, as others have theorised, he abducted her at SR123? (witness sees the BMW speed off). He takes her, maybe at knife point (or possibly renders her unconscious at the first opportunity, I.e. when he's sure no witnesses), takes her to a place he's staying at where he has the privacy to do whatever and a similar fate awaits SL as that of SB the following year. The difference I imagine is (and I don't have enough knowledge of the area of the SB kidnapping to know for sure abd someone I'm sure will put me straight if I'm wrong) the built up/busy area of inner London made things a bit more complicated and he had to adapt whatever plan he may have had to accommodate for this so had to work a plan to dispose of SL before leaving the area. Detective JD said there were warehouses round the canal area where it would have been easy to locate a trolley, or... if it wasn't JC then this could work too for someone who was just as cunning/charming, enough to hook SL, that he was a newbie and went with the flow. Maybe it's just me and my wild imagination, just trying to think of the possibilities. I'm no psychologist but it seems that JC and people like him have a need to do what they do and the more they do it the easier it becomes (becoming more experienced and nuanced with each kill). I don't think JC had killed up to that point or if SL wasn't him then possibly he was a robber and rapist who escalated over time until he killed SB. I still think it was him for now but I'm trying to keep my mind open to others. I read somewhere, someone likened JC to Bundy.
Sorry for the wild waffling, I didn’t intend to spew all of that. The thing I'm trying to work out is if the difference in the areas of the two murders had an impact on the the way they were carried out. Perhaps he thought he could afford to be more lax with with the 2nd one. Oh, I dont know, I think I've confused myself, I knew what ai meant. I need sleep.