We said little more as we walked along St Peter’s Street and into Thames Street. To the south I could see the cranes on the wharves and the river beyond, white with sails. Over to the west the sun was setting. Barak never broke his stride; he had spent all his life in the city and knew every street and alley. Eventually he stopped. A respectable-looking tavern stood where Thames Street intersected with a lane of narrow, tumbledown houses that led down to the river, some of the buildings slanting at odd angles as they had settled, over the decades, into the Thames clay. A little way down the lane I saw a sign marking another, shabbier-looking tavern, painted with the red-and-white cross of St George. It was the Sign of the Flag mentioned in the note.

‘Needlepin Lane,’ Barak said. ‘Mostly cheap lodging houses. Let’s go in here to this tavern; sit by the window.’

The place was busy, mostly with shopkeepers and workers come for a drink at the end of the day. Barak got two mugs of beer and we took seats with a view of the lane; the shutters were wide open this hot evening, letting in the stifling dusty stink of the city. We had scarcely sat when Barak rose again. A solidly built man in a London constable’s red uniform, staff over his shoulder and lamp in hand, was walking by. Later he would patrol the streets to enforce the curfew. Barak leaned over. ‘Your purse. Quick!’

I handed it over. Barak darted outside and I saw him talking with the constable, their heads bent close. At one point the constable turned and stared at me for a moment, then he walked on down Thames Street. Barak returned to the tavern.

‘Right,’ he said, taking his stool. ‘I’ve squared him.’

‘I didn’t see money pass.’

‘He’s good at passing coins unseen. So am I. I told him we’re on official business about some stolen jewellery, and we’re meeting an informant at the house two doors down at nine. Asked him to be ready to come to the house with anyone else he can muster, if I shout.’

‘Well done.’ I knew nobody better at such tasks; Barak’s instincts were always extraordinary.