I agree with your take on DV’s book, it tells a story, but I expected it to be inline with the way AS’s book.I don't think she did make a 6pm appointment to fetch it, she just said she would be along later that day.
Was it reported anywhere that she said 6pm? The diary appointment does suggest that she could not have gone at that time, but that isn't an issue given that the pub was open until 11pm. I don't think that there is really compelling evidence to suggest that SJL went to the pub that lunchtime rather than the place she said she was going. I know DV tries to make a case for it, I've read his book twice, but he is relying on two things:
1. Trying to claim she didn't take the keys for 37SR which relies on the Sturgis staff being really dim, and the police being the same--sorry, that doesn't really hold water to me. It also relies on the dubious idea that the door did not appear to be damaged in the press photos from a couple of days later. That is also really not very convincing.
2. Trying to claim that she had no other time to get the diary that day because there was an appointment in her diary for 6pm and that she must have been playing tennis at 6pm (at an unspecified location with an unspecified person who never came forward and her kit was in her flat, based on her unreliable mum's telling a radio journalist that she was). Pubs open until 11pm, it was near her house. She could have done the appointment, played tennis and STILL got the diary.
I think DV is not a reliable narrator. I wanted him to be, but I don't think he is. He seems to have a personal issue with the Met, and that is colouring his actions. I think he does bring some interesting info in his book but it might not be what he intended-- e.g. the officer he spoke to when presenting the evidence revealing that the police talked to the interim landlord and his wife and that the pub was open that lunchtime. Anyway, I don't think there is a huge conspiracy here to cover up...something... just a sad case of ambiguous loss (no body) and so no conclusion to the case, and the police can't reveal all the evidence because that is standard practice. Not everything is in the public domain.
What does not add up is the Mets attitude towards DV. They seem to dislike him, probably because of his criticism of their handling of the investigation.
With that in mind if they’re so sure he’s wrong why not just prove it. Search the PoW & the embankment and effectively close down any speculation that they got the investigation seriously wrong.
Best guess has to be they’re worried DV might be right.