Nightingale had the lamb in wild lemon and I made do with a chicken Madras hot enough to make Nightingale’s eyes water. It was a little on the mild side for me. Indian cooking has no terrors for a boy raised on groundnut chicken and jelof rice. The motto of West African cooking is that if the food doesn’t set fire to the tablecloth the cook is being stingy with the pepper. Actually there’s no such motto – from my mum’s point of view it was simply inconceivable that anybody would want to eat anything that didn’t burn the inside of your mouth out.

We ordered a beer while we waited, and Nightingale asked me how my diplomatic efforts were progressing. ‘Leaving aside your little contretemps with Tyburn.’

I told him about the visit to Oxley’s river and Beverley’s response. I left out the whole wanting-to-jump-in-myself aspect of the visit. I said that I’d thought it had gone well, and had established that there was a mutual connection between the two sides. ‘It’s something we can build on,’ I said.

‘Conflict resolution,’ said Nightingale. ‘Is this what they teach at Hendon these days?’

‘Yes sir,’ I said. ‘But don’t worry, they also teach us how to beat people with phone books and the ten best ways to plant evidence.’

‘It’s good to see the old craft skills are being kept up,’ said Nightingale.

I sipped my beer. ‘Tyburn’s not a big fan of the old ways,’ I said.

‘Peter,’ he said. ‘Of all of Mother Thames’s children you had to pick a fight with Lady Ty.’ He waved his fork. ‘That is why we do not throw magic around until we are trained.’

‘What was I supposed to do?’

‘You could have talked your way out of it,’ he said. ‘What do you think Ty is – a gangster? Did you think she was going to “plug a cap” in your head? She pushed you to see where you’d go and you blew up.’

We ate our curries for a while. He was right – I’d panicked.

‘It’s “popped a cap in my ass”,’ I said. ‘Not plugged – popped.’

‘Ah,’ said Nightingale.

‘You don’t seem that worried about it, sir,’ I said. ‘The Lady Ty business.’

Nightingale finished a mouthful of lamb and said, ‘Peter, we’re about to offer ourselves up as Judas goats to a powerful revenant spirit who’s killed more than ten people that we know of.’ He dug into his rice. ‘I’m not going to worry about Lady Ty until after we’ve lived through that.’

‘If I remember rightly,’ I said, ‘I’m the Judas goat, the “constable” in this scenario. And considering that it’s my backside hanging out in the air, sir, are you sure you can track him?’

‘Nothing is certain, Peter,’ he said. ‘But I’ll do my best.’