Of course he is being exceptionally economical with the truth, being selective and interpreting others statements to put his own spin on events, intent, thoughts....he has a vested interest financially and personally to undermine the case that JC is the "only suspect".
There is significant circumstantial evidence against JC and witness evidence that supports events in Shorrolds Road. There is no direct evidence that JC came into contact with SJL....maybe this is what he means, albeit in an opaque way.
DV has no evidence to support his theory. The evidence is that SJL was going to the PoW sometime after 18:00, not earlier.
The only way DV can offer up his theory is to dismiss and denounce the evidence that diverts attention away from it.
However, he cant offer any evidence of his own to undermine what the police have. Neither can he offer any evidence to support his theory
The investigation is still unsolved and is still subject to further investigation. Confidentiality has to be maintained as with all criminal investigations. There are witnesses, confidential sources, police intelligence, police methods all contained within the investigation.
DV sets up his book to lead the reader to a certain conclusion. I think he is actually quite clever in how he does it--he presents witnesses in such a way as to lead you to think that they are weird or odd in some way, words he uses himself a lot to describe them. HIs interview with the temp landlord is the best example of this as he presents him in a very negative light. It is not a neutral presentation at all. I have no idea what his motivation is. He claims to have spent a fortune on his investigation and I beleve the book is self published so he had no advance.
He sets up his book to try to demonstrate that (1) SJL was not going to 37SR and (2) her appointment with Kipper was faked so she could go somewhere else (3) which he decides can only be the POW and then (4) presents the interview with the temp landlord to set him up as being somehow dodgy and basically accuses him of murdering SJL although he is careful to hedge this by not overtly saying it--probably he has had legal advice (which is not cheap).
For him to have a reasonable go at (4) he has to destroy the 37SR working police theory.
His reasonings are:
(1) SJL "never took the keys" which is based on his hypothesis that the police did not have to break in to the property, which he bases on a press photo of the door, and the former owner of Sturgis telling him that normally there was only one set of keys per property.
For this to be true, we would have to have the Sturgis staff be either thick, lying to the police (because if they knew there was only one set of keys and they were in the office, they would have had to lie to say SJL took them), and all the staff conspiring to continue the lie, and/or the police being bumbling idiots who were all recruited from various village idiot competitions.
He also dismisses all the witness sightings (one dismissal involves him trying to locate one of the unemployed males who were on the street at the time of SJL's appointment at SR, because they were attending or returning from collecting benefits). He cannot locate the male but locates someone with his name at an address via the electoral roll and talks to a female at the address who says she has no knowledge of the male ever living there, DV dismisses this as the woman lying and gives the impression there is some dark nefarious reason for it (either she is telling the truth and has no knowledge of the male who may or may not be the same person as the witness from 30 years ago or she didn't want to talk to some rando who knocked on her door and was a bit persistent). Either way, this is meaningless.
(2) He bases this on the name being most likely fake, no record of the person in Sturgis files. I also think there is no real live person called Mr Kipper but this does not mean SJL did not go to 37 SR with the intention of meeting someone there.
(3) I think his reasoning here is not very convincing. We don't know everything about SJL's life so if she were not going to SR that does not mean she was going to the POW, she could have gone literally anywhere. He decides she is going to the pub because picking her diary up cannot wait until after she finishes work. To boost this theory he relies on a radio interview with DL, who he elsewhere slams as being totally unreliable, who says SJL was planning to play tennis that evening. I really don't think that this is at all reliable and no one ever came forward to say they had plans to meet SJL that evening for tennis or anything else.
(4) I'm not impressed with him setting up an easy to find, real person as a murder suspect. He should know better than that. His interview with the temp landlord was disrespectful.
Again, I don't know what DV's motivations are but they seem more complex than just him wanting to find SJL. I am sure he wants to find SJL, I don't doubt that. But he has some deeper, probably personal, issues with the Met, I would suggest. What they are and why-- no clue.