Those who have read Julia Blackburn’s agonising memoir of her sort-of-loved but truly awful parents will understand why the adult Julia has needed to get far away from them, in space and in time. The subjects she has chosen for her books have carried her as far as St Helena and the deserts of Australia, and taken in obscure 19th-century figures, such as an early conservationist who fought Victorian pollution and a little-known Norfolk fisherman who, in sickness, took to painting. Woven into this last book was the story of her own relationship with the Norfolk coast and the death of her second husband, Herman.

In Time Song she returns to the East Anglian coastline and Herman is, again, both a presence and an absence, but time now takes on a new dimension. Starting on a beach called Bawdsey, she notes the remains of a Martello tower from two hundred years ago and also the wrecks of pillboxes dating from the world wars of the 20th century. But she then makes a vertiginous leap back to when the entire area that is now the North Sea was covered by subtropical rainforests and mangrove swamps populated by creatures both like and unlike our turtles, crocodiles and rhinos. From then on, much of the book is a breathtaking survey of ever more distant eras and of the recent discoveries that have driven our perception of the dawn of our own race further and further back in time.

She has sought out the people who came upon the Pakefield flints in a river deposit near a holiday camp and a rubbish dump. These stones show evidence of having been being sharpened 700,000 years ago, far earlier than it was previously supposed that