It was Meg Simpson’s turn to redden. She didn’t like to be lectured by anyone, but she was on shaky ground and she knew it. ‘I’m not saying I won’t write the letter and authorize this operation, just that I need more. If you can find further detail on the context, on what is really going on in Moscow, then I would feel a great deal more confident. Has there really been a putsch? If you can confirm there has, without equivocation, then I guarantee I will sign that letter.’

To Kate, this information seemed theoretical at best, irrelevant at worst, and she could see Sir Alan felt the same, though he chose to internalize his anger, in front of the group at least. He stayed behind as she, Suzy and Ian filed out.

They didn’t speak until they were on the Mall. Suzy ordered a taxi and Ian let her climb in before he turned to Kate. ‘Do you fancy walking back?’

Her head was so paralysed now with sleep deprivation, coffee and the strange tension of that meeting that she had already decided as much. Not that she would normally have welcomed Ian’s company.

It was a lot warmer that morning, the daffodils blooming in St James’s Park, which was more or less deserted. They were level with the great expanse of Horse Guards Parade before Ian finally blurted out what was on his mind. ‘Have you spoken to her?’ he asked.

‘Who?’

‘Julie, of course!’

‘About what?’

‘Don’t be obtuse, Kate.’

She tried to think of any subject she less wanted to discuss with him. ‘What was that all about?’ she asked, gesturing back to the foreign secretary’s residence behind them.

‘You know what it was about,’ he said. ‘The Russians love playing games and sooner or later we need to stop responding. I just don’t agree with you and Alan on that, but it’s an honest difference of opinion and I’m perfectly entitled to express my views, convenient or not. Isn’t that his mantra? “We are not here to agree”?’

‘This is different and you know it.’

‘You both think it is. But I’m less certain. I don’t blame her for her caution. You’ll probably get your letter, whether it’s a good idea or not, but she’s just covering her arse. I don’t see any harm in making us go through the hoops.’

‘We have a week at most until the offer disappears – perhaps to a rival, who may be in a position to embarrass us.’