Suzy took a folder from her shoulder bag and placed it on the walnut coffee-table. It sat there like an unspoken accusation.

‘Tea, coffee, a drink?’ Simpson asked.

‘No, thank you, Foreign Secretary.’

They waited. Suzy was enjoying her moment in the ministerial limelight. ‘Get on with it, Miss Spencer,’ Sir Alan said.

Suzy glanced at Kate nervously. Whatever she was doing, perhaps she was having second thoughts. ‘I’ve been looking at the Operation Sigma file. It was extraordinarily well conceived and carried through, so none of this is meant to be a criticism in any way, but rather a reflection of the fact that we all know some things are bound to be overlooked in the heat of the moment.’ Kate kept her eyes on her new deputy. ‘I agree with Kate’s analysis that many of the facts do fit the idea that her husband, Stuart, was Viper. While he did not know the details of the original operation in Istanbul, he was aware that it was a significant success and he clearly had some general idea of what it was about.’

Kate could feel her face reddening. In reality, Suzy was protecting her here, since she had clearly worked out her boss had been somewhat economical in the file as to how much she had shared with Stuart.

‘So, assuming Stuart passed on to his controllers the fact that Kate was returning to Greece to continue with the operation, that might well have been enough for Moscow to swing into action and put a team on her tail. Until this point, Stuart as Viper adds up.’

She flipped open the file and handed around some sheets stapled together. ‘I’ve run a precise spot check on Rav’s phone for the last twenty-four hours of his life, including the time he was in Geneva investigating the lawyer with close links to the Kremlin. As you can see from this timeline, there was virtually no activity. He was entirely off the grid. There is the call to the Guardian journalist, which Kate reported. I have spoken to the journalist in question directly. He seems a pretty straight guy and insists Rav just wanted the lawyer’s name and told him nothing of what he was up to. He insists he spoke to no one about it and I’m inclined to believe him. Then there is the incoming call from Kate while Rav was in Geneva. After that, there are no calls and no spikes in any kind of electronic activity, save for here, at around six p.m. I think that’s the message that Kate also logged in the file.’

Kate handed her sheets back to Suzy. The others followed suit, as they contemplated their contents in silence.

‘I’d also say Rav strikes me as much too experienced and talented an officer to have breached operational security in any significant way,’ Suzy added.

‘Perhaps he was followed,’ Simpson said.

Kate glanced at Suzy, who waited for her to answer. ‘That kind of surveillance requires a great deal of manpower, ma’am. And, as Suzy says, Rav was experienced enough to have taken anti-surveillance measures and to have reported any activity back to us in London.’