Investment banker James Walker leads a double life. Despite his demanding job and being the dad of three young children, he is on call 24/7 as a volunteer with London Search and Rescue. It means scouring parks, woodlands, streets – and even rivers in a kayak – for missing people. And when he’s called on for help, it takes priority over everything. James, 41, says: “When the call comes through, it overrides all the settings on the phone so you can have your phone on silent and suddenly that