Two figures kneel side by side as the waves crash on to the shingle a few feet away. The North Sea is wild today, slabs of bronze- and pewter-coloured water slamming on to the shore and exploding into opaque foam. The kneeling figures hardly look up from whatever they are doing, but from time to time one will lean close to the other’s ear and they’ll shake with laughter.

Lida Lopes Cardozo Kindersley and Els Bottema grew up together in the 1960s in the Dutch city of Delft. The girls met, aged five, when Els would go to Lida’s house during school lunchtimes. As soon as they’d eaten, they would creep into the large abandoned garden that adjoined Lida’s backyard. It was in this secret, overgrown realm that their friendship was cemented. They climbed copper beeches, dug “bear traps” and fended off invaders with a homemade bow and arrow. When they found a dead bird, they would bury it, adorning its grave with the broken shells that covered the garden’s paths. What did the garden represent for two five-year-old Dutch girls at the start of the 1960s? “Freedom,” says Lida firmly. “Freedom.”

Approaching their teens, the two girls “slowly lost each other”, as Els puts it. “I lost everybody,” says Lida sadly. “I had very much landed on the wrong planet.” At the age of 19, she attempted suicide, only to be discovered because of the chance return of housemates. “You were not in my life,” she tells Els. “I wouldn’t have done it, probably, if you had been.”