I am loathe to add to the speculation on here, but something someone said earlier made me look again. The aircraft appears to have made it to the runway. As all of us who've operated in Cat 3b conditions know, it is often difficult to taxi when its really thick pea soup. Perhaps they did land but the runway viz closed in and caused runway excursion at high speed or disorientation just prior to touchdown? I can imagine that suddenly hitting a wall of fog on landing could have caused some issues. And they do appear to be roughly the right distance from the threshold. Will be interesting to read the report.