Tibbot met my eye and I steeled myself, hoping it was time to return to the question that I most needed answered. ‘Rachel, was Nick involved in what you were doing?’

‘Nick,’ she whispered.

‘Yes.’ I spoke slowly, deliberately. I had to know. ‘Was Nick Cawson involved? Please tell me.’

‘Nick.’ She opened her eyes and looked sadly at me. ‘He ran it all.’

My heart fell to pieces. And for a second I wondered if I were really the one who was mad for refusing to acknowledge what should have been obvious from the beginning.

She was still speaking. ‘I told that policeman about them,’ she said thoughtfully. ‘Taught the bitch a lesson.’

Coming to my senses, I began to argue with her, as if she would change her story. ‘But Nick’s not in government. What could he do for the Americans?’ I said.

‘He knows people, doesn’t he?’ Tibbot said quietly. ‘Doctor to people.’ And I realized something: that Tibbot had suspected this for a while, keeping it from me so that I would hold on to some hope.

Of course it was true. Nick had been angling to make contact with Ian Fellowman, Burgess’s Assistant Secretary at the Ministry of Information, with a view to becoming his doctor. If he had succeeded, how the CIA would have loved knowing those men’s state of health, what medication they were on, whether they were feeling stressed, whether they were going abroad the next month and where.

My fingers slowly scrabbled on the table surface. ‘Was anyone else involved with you?’ I asked.

Tibbot put a hand up to stop her answering. ‘We don’t want to know,’ he said. ‘Safer for them and us. It doesn’t matter now.’ And he was right: it didn’t matter now.

Then, without warning, Rachel’s hand flew across the table and snatched something. Before I knew it, she was leaping to the side, out of Tibbot’s reach as he grabbed for her and I saw what she had: his lighter and a page torn from his notebook screwed up. In a second the paper was alight and she was throwing it at the window in the door. As it left her fingers, Tibbot managed to grab her arm, but it flitted and flickered through the air. It meant nothing as a weapon, but as a little act of defiance it meant everything. The door flew open and Larren entered with three orderlies. One pushed Tibbot aside, while another rushed behind Rachel and dragged her arms back. She meekly let him. ‘I don’t care if you are the police,’ Larren barked. ‘She’s going back to the lock ward.’ Another orderly produced a gag, which he attempted to tie across Rachel’s mouth. ‘And if you want to speak to her again, you had better bring a warrant with you next time.’