Mama Thames reached out and patted me on the knee. ‘This was the old bridge, the one that was sold soon afterwards to that nice American gentleman. Now there was a man who knows how to show a river a good time. Two barrels of Guinness and a crate of Rhum Barbancourt, that’s what I call an offering.’

There was a pause while Mama Thames sipped her tea. Beverley entered with a plate of custard creams and placed them within easy reach. I had a biscuit in my hand before I realised what I was doing, and put it back. Beverley snorted.

‘In the middle of the old London Bridge was a chapel, a shrine to St Birinus and I thought, good Sunday Christian that I was, that this would be the right place to jump off. I stood there looking west just as the tide began to turn. London was still a port back then, dying but like an old man with a long, exciting life, full of stories and memories. And terrified that he was going to be old and frail with no one to look after him because there was no life left in the river, no Orisa, no spirit, nothing to care for the old man. I heard the river call me by the name I have forgotten and it said, “We see you are in pain, we see you are weeping like a child because of one man.”

‘And I said, “Oh, River, I have come such a long way, but I have failed as a nurse and I have failed as a woman and this is why my man does not love me.”

‘And then the river said to me, “We can take the pain away, we can make you happy and give you many children and grandchildren. All the world will come to you and lay its gifts at your feet.”

‘Well,’ said Mama Thames, ‘this was a tempting offer so I asked, “What must I do? What do you want from me?” And the river answered, “We want nothing that you were not already willing to give.”

‘So I jumped into the water – splash! And I sank all the way to the bottom, and let me tell you, there are things down there that wouldn’t believe. Let’s just say that it needs to be dredged and let it go at that.’

She waved her arm languidly towards the river. ‘I walked out of the river over there on the Wapping Stair where they used to drown pirates. I have been here ever since,’ she said. ‘This is the cleanest industrial river in Europe. Do you think that happened by accident? Swinging London, Cool Britannia, the Thames Barrier; do you think that all happened by accident?’

‘The Dome?’ I asked.