So whoever kills her, and realises he needs to get rid of her car, doesn't even have to look far to find it. It's the Ford that the keys fit. It's probably the first one he sees, helpfully confirmed as a woman's by the straw hat, and as the right one by the keys fitting and the purse inside.
And, if the perpetrator did not know SJL's car beforehand, the place it was parked would be (1) near to the place where she went inside to encounter him/with him (2) not in a very public area where there were pedestrians and other motorists who could see and remember him getting into it (i.e. if I were stuck behind a double parked car during my lunch hour when I had limited time, I would likely remember the bloke getting into the car, faffing around putting the seat back, etc).
If the perpetrator knew SJL and knew her car then this is easy of course, although he still has to be careful no one sees him getting in.
And yes, if she used Shorrolds as a cover story to go and do something else, whatever she went to go and do had to be a quick errand, or the Shorrolds story isn't going to hold water. Since she made a cover story it had to be important for her to do so, she couldn't just go out without having a work related reason to do so. Actually an argument against her planning to go to the pub to collect her items is that she didn't take her bag, because if she came back to the office clutching those items she might be asked about them. However, she could have left them in her car underneath something, or just dropped them at her flat as it was so close. So it's a fairly weak argument against.
If SJL told her colleagues about the diary and chequebook and the pub, as surely must have been the case, what was the reason the police dismissed the pub as a possible location for her to have visited? Or tried to visit?
I think too much is made of the "perpetrator needed a motive" idea when in reality most murders are spur of the moment. The "motive" is often the perpetrator's instant rage/lust right before.
One thing that stuck out for me in CV's interview with DV was the way he remembered where the diary and chequebook had been placed in the pub, he said that of course SJL could not have been because the chequebook and diary were still in the cellar, or on a shelf on the stairs down to it (seems an odd place to put lost property but maybe that's the safest). This incident was decades ago in a pub he lived in for 6 weeks, then was at for a few days. Yet he recalls where lost property, specifically SJL's, was put? If he worked there for years then I would not be surprised he remembered but so much has happened since then so why recall this trivial detail? I think either he has an exceptional memory or this incident was very important to him, perhaps because of all the publicity around it and him thinking about his being involved albeit on the periphery.
I don't think there is a complicated plot here involving multiple people, decoy cars and other Hollywood movie plot devices. SJL went out, encountered someone--either someone she knew and planned to meet i.e. a boyfriend, someone she knew and didn't plan to meet, or someone she just came across while running her errand. Went inside somewhere, for some reason, and something happened because whoever she met probably either tried it on with her, or decided having found himself alone with her, to assault her. It would be appallingly tragic in the extreme if this case is never solved because the police believed in SJL's flimsy cover story excluding all other hypotheses, and DL encouraged it because of her strict religious beliefs and the fact that she didn't want the public to think badly of SJL.
