Time and robbery

Time and Robbery features the protagonist of Ore's Centuries Ago and Very Fast, Vel, a gay immortal born in Paleolithic who jumps time at will. Unless Vel can help out his younger self, Vel's tribe's descendants—a big chunk of the 21st-century British population—will be eliminated from the timeline. Present-day Vel, though, has problems of his own, so he takes a chance and outs himself (and his talented teen-aged daughter Quince) to Joe Tavistock, a subcontractor on the weak end of the plausible deniability chain dangling off British intelligence, making it Joe's problem. Joe's superiors are dubious, and Joe doesn't know who to trust. The stakes are high not just for Vel, but for everyone involved.