Perhaps, when she next saw Morahan, she might ask him whether he had reason to suspect that anyone on his staff was operating to a different agenda. He’d probably look at her with mystification. If he did, she could just about imagine herself showing him the text. She could already hear his reaction – don’t worry, some idiot…

She was going round in circles. She could never, and would never, tell a single soul about the 2005 text. She had set that in concrete when the Met detective called on her a few weeks after 7/7. He knew only that she, like many others, had attended meetings where people now of interest to the police might have been present. She said she couldn’t help him; she recognised none of the names he raised. He had no reason to doubt her.

The questions the text raised, the guilt it ignited were impossible, unthinkable to admit to anyone but herself. At that crucial moment, however much she could be forgiven for not instantly interpreting it, she had, as it turned out, failed in the most devastating possible way – a failure she’d carried like a death row prisoner’s shackles ever since. The texts, past and present, were a weight she must bear alone. The only means of sidelining them was to focus single-mindedly on the task ahead.

Trying not to catch Patrick’s eye she retrieved from her bag the Sayyid folder Morahan had given her. Wherever they now were – if they were even still alive – the five individuals named in the files all hailed from the town of Blackburn in East Lancashire. The files shared the same template, headings running vertically down the left column. The left heading was TOP SECRET, right side OPERATION with the following word blacked out. The next line began KV2 followed by a further redaction. The headings below ran: PICTURE; NAME; DOB; LOCATION; PHONE; HOME ADDRESS; FAMILY ADDRESS; FIRST CONTACT; CURRENT STATUS; NOTES; HUMINT; COMINT; LAST CONTACT; FILE STATUS.

One name was Samir Mohammed. His photograph showed a young Asian, probably taken in his late teens. Date of birth was 12 October 1987; home and family addresses the same number and street in Blackburn; current status ‘inactive’; file status ‘Closed 31 December 2006’. One entry withstood clear interpretation. Humint read ‘Contacts not pursued after closure.’

Assuming he was alive – and had not since been involved in anything of interest to the police or intelligence services – Sara judged that he might be the easiest to approach. Whether or not he still lived in Blackburn was unknown. There was no hint of what story he, or any of the other four, might have to tell.