Anna lifted the tape and stepped over one of the sections of wall, hearing the throaty sound of other pigeons unseen in their shelter among the ruins. She was standing in what must have been a long room. Whatever it had once been used for, its character now was quite lost. Had there been beds in this part, or were the wards only upstairs? Was this a dayroom? Squatting down at one end, she could see patches where the texture of the wooden floor showed through the silt of ash and plaster. She stroked the wet grain of it with her fingers, a tiny contact with Arden’s past. With Olivia.

Ignoring the tape, she scrambled over the remains of the inner wall into the quadrangle. The hospital had been arranged in two separate halves, the men’s and women’s sections, each with their own airing court for daily exercise. There was the remains of a circular path, now colonized by weeds and made from uneven segments of stone, a tree stump in the middle. Following the path round, she stumbled over tufts of grass and groundsel. She stood looking at the ruined walls and the slit-eyed water tower.

The airing court. Their light on the world, this enclosed rectangle of sky. Images from Olivia’s strange, disconnected account of herself filled her mind. How had she felt that June morning, moving along the drive towards this hospital? Was the sun shining, sky an exuberant spring blue and the leaves new and bright? She had not mentioned these things of course. Perhaps she had seen nothing. They arrived from Birmingham by ambulance, closed in, probably dark inside, Olivia sitting or lying in the juddering, gloomy space, watched over by iron-faced orderlies. Had she been tied in: strapped? How had they restrained her frail body? Perhaps they had already tamped her down with phenobarbitone so that she knew little of the journey. Or had her brown eyes had to face, wide awake, this place of lost souls, of strange cries and wild movements?

‘I thought, when they took me there’ – Anna heard the words in her mind – ‘that I was going to my death. They would have absolute control over me. They proposed to bury me alive . . .’

Anna began to cry, the sadness of the past days swelling in her at the sight of these remains: hundreds of square yards of stone and brick which had been the crucible of so many lives. Raindrops on her cheeks felt cold compared with her tears. She turned her face to the sky.

She had never seen Olivia, yet she had learned, through her childhood, to love her: her mother’s friend, beautiful and tragic, their affection for each other passionate and sparkling as a fairy story. The mention of her brought a special light in to her mother’s eyes. Kate and Olivia – best friends. Ordinary but magical. Olivia enshrined as something Anna longed for. She was more than a girl who had been a friend: she was friendship itself.