‘No, but when I had time to reflect, it was the only explanation that made sense.’ She forced another smile. Given they all knew that Grove’s sole aim here was to bury this file in the darkest recess of the Service’s vaults, her show of probity was beginning to grate. ‘You know as well as I do, Mrs Grove, that in our world we never get hard and fast answers. There is no black and white. When you have ruled out all other potential explanations, what remains is the truth, however unlikely. Upon reflection, I decided Ian had been right. I feel no shame in admitting it.’

‘So you accept this matter is closed?’

‘Absolutely.’

‘Good. Good.’ Grove nodded sagely. ‘We appreciate your cooperation, Mrs Henderson. I know this has been a tough time for you.’

‘And the prime minister.’ Grove looked confused. ‘I mean, to have been falsely accused in this way,’ Kate said. She was laying it on really thick now, but why not? She might as well enjoy it.

She glanced up at the light above her, in which she suspected a microphone was hidden. Whoever was listening – MI5, certainly, perhaps even the prime minister himself – she hoped they appreciated the effort she was putting into her show of contrition.

‘Yes, yes. Monstrous. Very difficult.’ Grove stood. ‘Thank you, Mrs Henderson.’ She offered her hand. ‘A relief to all of us, I’m sure, to have this matter finally resolved.’

Kate took the proffered hand. She even kissed Suzy, though she didn’t grace Ian with an answer when he asked her in the corridor outside how it had gone. Let his ambition sweat a moment longer.

‘Kate,’ he said, as she turned her back on him. ‘Thank you for your contribution.’

She faced him. ‘To what?’

‘This inquiry. And the Service, of course.’

‘Is that some kind of joke?’

‘No, no. I wanted to thank you for all you have done.’

Kate retrieved her bag and walked away, without bothering to offer him a reply.

She found Julie waiting for her by the lift. ‘Don’t,’ Kate said, raising a hand to forestall any show of emotion, for which she no longer had the stomach.

‘I’m not going to cry,’ Julie replied. ‘Not now, anyway.’

‘One day soon we’re going to meet up and get very, very pissed. And we’re never going to talk about any of it again.’

‘You did the right thing, Kate.’

‘You don’t think that. And I’m not convinced I do, either. So I need to get out of here before I change my mind.’

‘I do think it, actually.’

Julie launched herself into Kate’s arms. They held each other until Kate released herself and belted for the stairs before the emotion welling inside her could find expression. She was damned if she was going to be seen leaving the building for the last time in tears.