She went up to her bedroom, drew the blinds, sat down at her desk and pulled the package from her bag. Angrily she unfolded it and removed the wrapping paper to reveal an envelope. She slit it open. Inside was a photograph – no note or message accompanying it. She felt further inside and retrieved two small objects – an audio cassette and dictaphone.

Yes – the final delivery.

The photograph was grainy, the expressions unreadable – a photograph that had been taken without the knowledge – or consent – of those in it. Despite its murkiness, she recognised it and the restaurant setting instantly. She inserted the cassette into the player and began to listen. Not that she needed to – the memory of that evening was clear as forked lightning. An icy foreboding was beginning to give way to the dawning of a terrible comprehension.

She checked her watch – time to leave for Kennington. She was in no state to answer questions – whether from Patrick or the detective. Should she phone to cancel? No. It would only raise alarms. She must tough it out. She went into her bathroom, roughly splashed and rubbed her face, reapplied make-up. She brushed her hair, glared at the mirror and forced her face to enact the shape of a cynical lawyer’s smile.

She returned the photograph, tape and player to the envelope, folded it back into four and selected a location for it during her absence.

At Kennington Buttler led them into a scruffy office within CID; the detective was taking pains to avoid any suggestion of a formal police interview. When Sara had arrived with Patrick without any forewarning, Buttler had even greeted him as an old friend – perhaps he was canny enough to anticipate it.

There hadn’t been time for Sara to brief Patrick on her conversation with Iona Morahan. She had no intention yet – and until she’d worked out the possible consequences – of telling him about Sayyid’s second and third offerings.

Buttler sat them down around a scratched wooden table. ‘Apologies, I should have offered. Tea? Coffee? Biscuits have probably run out.’ His twinkling eyes were in full dance.

‘We’re fine,’ said Sara. Patrick cast her a quick look for her reply on his behalf. She lowered her eyes back at him.

‘Right,’ said Buttler. ‘I’ve got a note of the timings you gave me. Just one question. You said it was 8.30 p.m. that you received the text message from Sir Francis asking you to come back.’

‘Yes, around then.’

‘And it’s gone missing from your phone.’

‘Yes. As I said last night, perhaps I did delete it in all the chaos.’

‘It’s an odd one.’ He paused, apparently stumbling over a puzzle. ‘That sent message isn’t on Sir Francis’s phone either.’

‘What?’ The pinpricks of sweat returned. ‘He must have deleted it.’