At home, Iona’s bedroom light was off. He sat down at his desk and gazed blankly for a few seconds at the package, lifted it and turned it through 360 degrees. No words, no markings on the brown beneath the plastic. He slid the envelope out and opened it with the paper knife. He extracted the small pile of contents. They were headed by a note in the same font.

Dear Sir Francis,

Thank you for your response.

This initial package contains personal files on five young British Muslims.

I have made two redactions.

The first is the KV2 serial number. This is information you do not need and would present an extra danger both to you and me.

The second is the name of the operation this was part of. Later I may give you this name, though not in writing. Knowledge of it is the most highly classified secret of British intelligence both now and since its inception. It is confined to very few.

Nothing else is blacked out (unlike the intelligence files your Inquiry has so far received where redactions render them effectively useless).

Of these five persons some are, or have been, combatants, others not. Some have disappeared. If you wish to fulfil your remit, you must attempt to trace these individuals or their families and take evidence. You must not use police or intelligence services to carry out this investigation. Those channels are compromised.

Knowing the potential consequences, I need your confirmation that you wish to continue. I will then advise you on obtaining the help you need.

These few files that I have been able to give you are the tip of a large iceberg. They are also its inception. From them a decade-long pattern follows.

A final warning. Once you knock on the first door, you must move fast.

Sayyid

Morahan lay the note aside, absorbed the accompanying instructions and began to leaf through the files. They contained print-outs of photographs; phone call intercepts; logs of suspects’ movements. They were each headed by a brief biography containing a name, present suspected whereabouts, and previous addresses.

Who was this secret informant? Sayyid. Was he, or she, to be trusted? What position was he in to have access to raw classified files? If the operation he claimed to know of had really existed, how and why was he one of the few who knew of it? Were his warnings genuine or for effect?