I have to say that when reading HL2 again (or it could be no 1), Slemen talked about a bomb falling on Edge Hill and that lots of rats could be seen on Mason Street.
Although I really enjoy his stories, not only was he 20 years too late when giving a birthdate of Williamson but it would be virtually impossible for any amount of rats to run down Mason Street from the tunnels as no entrances were at ground level. Smithdown Lane I could understand but I think I can put this one as a 'fictional' story!