A t 56, I am running my first marathon, an old, fat, bald dad surrounded by millennials in body-hugging Lycra and smiles that look AI-generated. But I am ahead of them. For they are only competing for positions and personal bests, and I am being chased by zombies. The black dog of depression hit me around the time of my last birthday. I didn’t feel I had achieved anything of note for an eternity. I used to work out but, for years, work kept getting in the way. I decided to kill two circling, carcass-sniffing vultures with one stone and run my first marathon. I started off accompanied by audiobooks, but when Ben Elton’s autobiography got a bit whiny, I remembered Zombies, Run! – an interactive running game for smartphones that came out years ago. That became my running companion. You start in the ruins of a shot-down chopper, with the voice in your ears trying to guide you to safety through the ranks of the undead. The interaction comes via short sections where you are told to run fast rather than lope.…