Watch HDToday. Is there any way to slow or even prevent the ravages of time? Veteran presenter Johnny Ball looks back over the 45 years that Horizon, and he, have been on air to find out what science has learned about how and why we grow old. Charting developments from macabre early claims of rejuvenation to the latest cutting-edge breakthroughs, Johnny discovers the sense of a personal mission that drives many scientists and asks whether we are really any closer to achieving the dream of immortality.