In dirty Kilburn I parked the car on a meter and ran up the road. I found a shop and bought a packet of Bourbon biscuits and a bottle of Pernod. Then I jogged down the stairs to the basement door of the town-house.

‘Please,’ I buzzed the door, ‘please, it’s Rose Langton. I used to work for Xavier Smith.’

‘I’m shut,’ a disembodied voice said. ‘Go away.’

‘Please, Peggy. It’s so important. I wouldn’t bother you, but this one’s a winner. I swear.’

She opened the door a crack. I shoved the Pernod round it.

‘And I’ve got biscuits,’ I said, placatingly.

‘And hard cash?’

‘And hard cash.’

Muttering, she let me in. She was more blind than the last time I’d been here, and her glasses were milk-bottle thick, magnifying her grey eyes alarmingly.

‘Remember me, Peggy?’ I smiled as I pressed the Bourbons on her too. ‘Haven’t seen you in a while.’

‘They all come back,’ she said, seeming both cross and triumphant. The smell of cats in the warm basement was ferocious. ‘They realise the damned computer won’t reveal everything like some damned crystal ball, and they come sloping back.’

‘Of course they do,’ I soothed. ‘How else would we get to the bottom of things?’

‘No need to butter me up, my girl,’ she sniffed, but a small smile played round her wrinkled old mouth. Her lipstick was a startling orange. ‘I’m making chai. Want some?’

‘Love some.’ It would be undrinkable but worth it. ‘Thank you.’

‘What do you want?’

‘I’m looking for anything you’ve got on a man called Hadi Kattan.’ I headed to the end of the room that housed the 1990s through to the seventies. ‘Hadi, Ash and Maya Kattan – do those names ring any bells? London society pages, Iranian and possibly Saudi connections.’

‘Not off the top of my head.’ She put the Pernod on a shelf and pulled open a drawer. ‘But look in there. If it’s not in there, it didn’t happen.’

‘And I was also looking for a girl called Huriyyah something. Possibly the same family. Probable Oxford connection. I don’t know her surname, though.’

The kettle was whistling as I went through file after file, my hands shaking. I cut my finger on a piece of paper. Eventually I found Hadi Kattan. There was a piece on his rumoured involvement with the Iranian Secret Service, MOIS or VEVAK, from 1989 but it was largely unsubstantiated.

And then finally, I came across what I was looking for.