I wish I had started a timeline now, it makes it so much easier to look things up and remember them. Do we know if William came home before the trash collectors were refused entry, or afterwards? Even the most trusting person would have their suspicions raised if they came home to find their wife missing and the housekeeper forbidding entry to the basement.
Really, if the way we think this might have played out is correct, how horrific for Roy. Even if he wasn't aware or made to be involved in anything at the time, being questioned by police and just hearing the rumours would be enough to give a child nightmares.
In all the best stories of course, people leave confession notes on their deathbed explaining everything. Doesn't look like it happened here though. All three people who might possibly have known something are dead. Even the Russians William met will be too. Although if they were involved, they might have confided in others. So there is still a tiny chance there is someone out there with information.