Born to swim thousands of miles in the ocean, the giant sea turtles are now trapped in a tank of golden-green water at London Zoo.

But not for much longer. Two lonely people, a bookseller and a children's illustrator, have begun thinking turtle thoughts.

As they come together to hatch a plan to release the turtles into the sea, their diaries reveal how they find their own lives changing in imperceptible and quite unintended ways.