Obviously the big things CH discovered (TW’s diagnosis and the real reason they lost their home) are, and should have been checkable, as there will have been a substantial paper trail in both cases, but it’s less clear to me how someone at PRH could have checked that the second stint on the path was roughly as claimed in TSP, short of someone going into full-on private detective mode.
There’s an alibi for them having a single, crappy old phone they seldom charge, so no date-stamped photos, there’s no indication they had contact details for Dave and Julie, and the homeless wood dwellers, the homeless men they meet in Plymouth etc weren’t going to be contactable, and people carrying all their belongings aren’t going to hang onto hotel receipts, bus tickets etc. ‘Anna’, who doesn’t care how much rent they pay her, for a flat in a tourist area where she could make a small fortune from tourist lets? Tortoise man?
I agree that where they left the van is an excellent question, but PRH wouldn’t have known about the Parsons having encountered them walking in the wrong direction at the wrong time and documenting it on their blog.
Even if PRH had had a far high expectations of evidence than the vast majority of memoir publishers, the Walkers would have looked perfectly plausible if they’d said they couldn’t produce a single piece of evidence that they’d done the second part of the path as claimed, other than some notes on the guidebook.
(Does a bank statement show which ATM you withdrew cash from?)