What compulsion had made her even want to call by here? Patrick was all for going straight home and had encouraged her to do the same. Yet the journey felt somehow incomplete without returning to the surroundings she had committed herself to for the coming months. She had an urge to analyse, to theorise, to find from these first encounters a web which would form a structure; certainly to begin to build a chronology. The Blackburn group had attracted some kind of attention from late 2005 and through 2006 – the period after 7/7 when the security services, aware of their failings, were desperate to intercept new plots; to try new methods perhaps. Had they any inkling of the terrible experience Sami had suffered? Just say, after the questioning by Blackburn police about the girl, MI5 had succeeded in tapping up one of the group, why did none of the files contain any sign of it? Could it be that it was something too secret to be recorded on those files?

She was interrupted by a knock on the door, followed by Morahan poking half a head around. She looked up with pleased surprise. ‘Sir Francis, hello.’

‘Good evening, Sara, thought I heard footsteps but didn’t know you were back.’

‘We’d achieved what we could.’

‘Come and tell me all about it,’ he said with the warmth he always seemed to show her. There was the same sparkle too in his eye as when, during their first meeting, she’d suggested they were like spies talking on the Common.

He waved her to one end of the sofa and sat himself on the other. She compressed Samir’s story as concisely as she could, then the doorstep conversation with Iqbal Jamal Wahab’s father. She omitted the inconsistencies about Asif Hassan’s whereabouts.

‘Did you come to any general conclusion?’ he asked.

‘It’s sparse,’ she replied, ‘but I feel it indicates some element of central co-ordination that might challenge the received view of discrete cells or lone wolves being the sole MO of jihadis in the UK. Patrick is more sceptical.’

Morahan gazed out of the window beyond her into the gathering gloom and felt the back of his hair, stroking it down to the collar. She was unsure whether it was a mannerism or nervous gesture. Despite his friendliness, his experiences of sitting in a confined space with a young Muslim woman must be limited.

‘And how was Patrick?’ The question startled her; she’d assumed that he would follow the logic of the conversation and pursue the subject, not the person.

‘He was fine.’ She waited to see if he’d elaborate.

‘Good. Decent chap.’ The same words he had used before – no more.

If he wouldn’t, she would. ‘I can’t help wondering why he was chosen for this job. Wouldn’t a Muslim have been more suited?’