Thank you for your helpful thoughts, but this is Kent, England, MG. We have no "canyon roads" nor "wilderness" nor anything similar. I understand that Roger was depressed, but for no obvious reason of which I am aware, and I have heard that his medicine is not with him. Roger was socially normal (well, normal for a Morrisman and bird watcher) and in steady employment, which rules out Alzheimers.

I am sure he had a mobile phone. The North Kent marshes can be treacherous, but as an experienced birdwatcher I am sure he would not have been silly enough to try to walk on the ooze.