So… I was just rewatching In The Flesh (the fifth episode with Simon’s backstory) and I dunno if this might be true, but I was thinking.
Simon was the first to respond to the chemicals of Nortriptyline, the drug that ‘cured’ the zombies from their rabid state. And then I remembered that he had taken all sorts of drugs from categories ‘A-Z’ as he put it.
So maybe, just maybe.. that was what brought him back from his rabid state? Maybe the chemicals used to create Nortriptyline was triggered by some remnant of what Simon had taken years ago to kill himself. (If the body does still retain the cause of death even after decomposition.)
If that were true, then it’s mind-blowing cause the irony is just too much. And Dominic Mitchell is a genius!