There is a kind of uber-story about the future of ageing, regularly featured in the press, that swings through from the lows of crisis reportage (we’ll all be living longer, the pension pots will be empty, health services will crumple under new obligations to the elderly) to the highs of techno-euphoria (gene therapy and nanotech will enrich our late lives, we’ll be able to see our grandchildren’s children, work until we’re 90 and dodge decrepitude).