So summing up, it may or may not have been JC. And today, DV may be right or may be wrong.
After 35 years, are we any further on?
We are, I think, a little bit.
What DV has done is pretty much demolish the accepted narrative about SJL's disappearance. Essentially, there are now good grounds to think she never went to Shorrolds Road at all. Not the least of these is that the "reconstruction" produced no further information or sightings. Why not? Well, DV maintains, I think correctly, because what it depicted didn't happen, that's why not. You're not going to jog people's memory or get them to remember stuff that didn't happen. The Cannan stuff only started coming out
after he'd been named and is all single source (eg did anyone check this claim, with others imprisoned with him, that Cannan was called "Kipper" - or was that
one guy's claim based maybe on a grudge?)
So it now appears she went elsewhere. Here's where I differ from DV. His conjecture is that she set off instead for the pub where she'd left / lost her cheque book and diary.. The pub was closed for stocktaking, but five people were there: the departing tenant couple, the holiday cover tenant couple ("Clive Vole" plus partner), and the cellarman. DV thinks she got there, was killed there, was hidden under the false floor and is still there.
He has not, I am sure, put his whole case out there. But there's no more evidence for what he has said than there is for the JC theory. It's not clear she was deliberately lured to the pub - what does the murderer do when she turns up and four other people are there? It's not clear she's buried there, because as soon as the pub gets reconfigured she gets found, and when she was put there would be obvious from the clues DV relies on. What happens when the tenants return and do a handover stocktake of the cellar? What if the cellarman notices anything?
DV's suggestion also doesn't align with the likely most reliable sighting by BW. An equally plausible alternative, which does align, is that she was intercepted / abducted at her car in Whittingstall Road. Maybe that's the reconstruction they should have done. She never made it to that pub either and that's why she never picked her stuff up. She was made to drive elsewhere, and was seen doing so.
It could be that JC did it, because it fits his MO, but whoever did, it wasn't by meeting her at Shorrolds Road. Even if was JC, this assumption has ensured that no useful or accurate additional information that might convict him was received at the time.