‘Are you out of your minds?’ Grove asked, staring at them in cold fury.

‘We are investigating a case of possible treason,’ Suzy said, sounding defensive and uncertain now, as Williams and Young seemed to retreat into themselves, evidently unwilling to charge to Suzy’s defence. Kate wondered if Ian had told his lover that they had more top cover for this ambush than was the case.

She tried to hide her own sense of confusion as to where Grove really stood. Could it be the case that she had set this up and her outburst here was no more than a charade?

‘Mrs Henderson is leading an investigation at the direct instigation of the prime minister,’ Grove thundered, ‘who, last time I looked, was still the democratically elected leader of this country – with all the legal and natural authority that flows from it.’ Grove turned to her. ‘Mrs Henderson, you are free to go.’ She swung back towards Suzy. ‘As for you, Miss Spencer, and your friends here, one more step out of line and it is you who will find yourselves under arrest. Is that clear?’

Grove was damned impressive when riled. She seemed taller, more imposing. Kate followed her out. ‘Bloody jokers,’ Grove muttered, as they headed back towards the baggage reclaim area and the exit. ‘Ian Granger’s over-played his hand this time. You wait until the prime minister hears of it.’

Grove offered Kate and Callum a lift and suggested Kate hop into the back with her. As soon as the doors were closed, Grove turned to her. ‘I’m sorry, Kate. I got wind of it too late.’

Kate was gazing out of the window at the damp streets and the lights of the traffic refracted through the rain on the glass. ‘The Security Service knew about Agent Dante.’ Kate turned back to Grove. ‘How?’

‘I don’t know.’ She shook her head emphatically. ‘Truly.’

The car was silent but for the hum of the engine and the beat of the rain. ‘What did they ask you about?’ Grove went on.

Kate considered how much to tell her. Was Grove friend or foe? As this affair wore on, it was harder and harder to say with almost everyone involved. She looked at Callum’s dark curls brushing the ceiling of the car. Was it possible that he had told someone about Dante?

‘Ian and his acolyte Suzy have done a great deal of work to try to fit me up as Dante.’

‘What kind of work?’

‘They presented me with evidence that Sergei had attended a conference I was at in Sofia in 2012.’

‘I don’t understand why that is significant.’

‘Because I told them I hadn’t seen Sergei between the time I left Russia as a student and him turning up in London.’ Grove was still frowning at her. ‘If I was Dante, they would naturally want to assemble a pattern of clandestine meetings with contacts over a period of years. But I absolutely did not see Sergei at the conference, so either the still is faked, or he was there and I just didn’t run into him.’