The lake or pool might certainly exist in old iron workings, since even the modern coal mines had been closed down because of the expense of pumping. Whether the pool was or was not in a natural cavern seemed doubtful. The only essential question for us was why Marrin and his assistants did not talk about their excavations – probably for the same reason that they did not talk about their forest ceremonies. I might not be far out in my wild guess that they were introducing themselves to long-suffering spirits of lower earth.

In the early afternoon I set out for Elsa’s private dell and had trouble in finding it since I had been paying attention to her rather than the path she took. So I returned quickly to the track by which we had left Broom Lodge, waited for her and then followed her. It was not safe to show myself so near the colony and walk alongside her.

She was nervous and not very happy, once or twice stopping as if to return. That was understandable. I may have appeared to her a mere seducer anxious to keep our affair quiet and in no hurry to see her again. She had nothing to go on, knew not enough about me and was calling herself a sucker.

I had shaved, but otherwise looked what I was: a tramp in the Forest. The darling took command from the start, kissing me like a sister with her arms on my shoulders.

‘Piers, you needn’t be so proud,’ she said. ‘Why didn’t you tell me you had no money?’

It was, after all, an intelligent guess that I couldn’t afford an inn and I wouldn’t sponge on the colony. I was half tempted to let her explanation stand, for it would save a lot of trouble. On the other hand, she might quite easily ignore my demand for secrecy and tell her uncle that he was to insist on putting me up even if I refused.

What I did was to give her some account of my travels, which I had barely mentioned since the first dinner at Broom Lodge. When one is studying communities of the past, I said, one must live as they did to understand their economies. That was of course nonsense, but it sounded impressive and she cheered up.

‘Your Romans had hot baths, Piers,’ she retorted.

‘But the tribes of the Forest didn’t.’

‘Why don’t you try ploughing a field with a flint on the end of a digging stick?’

‘Unnecessary. I’d be more interested in the mining and trading of the flints.’

She accused me of being an absent-minded professor, and I asked her if she thought they couldn’t fall in love.

‘And then hide just round the corner for three days when they are supposed to be in Wales and don’t write or telephone!’

‘Of course I hid. I didn’t want you to find me smelling of old coal.’

‘I said leaves.’

‘You don’t mind that?’

She did not answer, but stood there, tall and serene, with her eyes on a level with mine, and no longer questioning, but surrendering.

When at last we drew apart from each other and lay side by side on our backs looking up into the approving, quivering canopy of leaves, my conscience pricked. I longed for the peace and passion of her to continue; they had and they would, but I felt like some spy who had learned to love with all his heart, disgusted that he must interrogate the girl who trusted him, yet determined to do so.

‘Does Simeon still try to spear salmon?’ I asked.

‘Not since the win on the pools. But he still goes out at night.’

‘Spirits of the deep?’

‘Something of the sort! I don’t understand that silly lot who treat him as an arch-druid. He shouldn’t put up with an inner circle like that in our colony. I wish he’d stick to meditation and past lives and all that.’

‘Perhaps he believes he’s an arch-druid?’ I suggested.

‘Well he can if he likes so long as he doesn’t try it on you and me and the rest of them.’

She knew very little of the sect and its activities. When one is young, there is so much one doesn’t notice – or can’t be bothered to notice – outside the play of characters and the daily complications of a job. If she had been told that her uncle chose to stand on his head and let gold grow out of his feet, she would have shrugged her shoulders, wondered what he was really up to and got on with mothering the colony and selling black puddings.

‘Do they ever go skin-diving with him?’

‘I’m sure they don’t. He likes to be alone. I was surprised when he took you down to the Guscar Rocks.’

‘So was I. He wanted to show me that it was not dangerous at slack water. But there can’t be many places where one can go in off the land.’

‘He has a boat – a little dinghy with an outboard motor.’

‘At Lydney?’

‘No. Higher up at Bullo Pill.’

It was mere chance that she knew where it was. The boat came from a barge which was being broken up. Marrin had paid cash for it and the transaction should never have appeared in the books at all; but the buyers’ receipt had accidentally passed through her hands, stating the price of the dinghy plus delivery at Bullo. She didn’t know if it was still there.

‘That was before he took to his goldsmith’s work?’ I asked.

‘About the same time.’

The scanty evidence suggested that he had bought the boat after he had found the hoard and because it was easier or safer to transport the precious objects by water rather than by land. In that case where was it? The grave or treasury could not be underwater since the level of the Severn would not have changed much in the last fifteen hundred years, though its course certainly had. So it must be in some place where there had been dry land at the time, say, of the worship of Nodens and which was underwater now. Yet there were few if any such places. Everywhere the flood plain of the tideway had been wider than now.

Well then, Marrin might have discovered the hoard in or on the banks. Very unlikely. No one would bury a chieftain and his treasure where an exceptional tide might sweep the lot away. I came to the conclusion that boat and hoard had nothing to do with each other. Marrin continued to use the boat because he was fascinated, spiritually and physically, by life beneath the waters.

My darling abbess more easily accepted my explanation of leading an iron-age life. The fact was, I think, that she found our woodland love-making so precious and romantic that not even Uncle was to be informed of my secret presence. We agreed to meet again, and after that I would soon reappear at Broom Lodge as a respectable townsman. The distressing thought occurred to me that, if I did, Simeon Marrin’s fate would be in my hands. Attempted murder need not for Elsa’s sake be followed up, but the monstrous destruction of a treasure – or, as the major feared, the production of fakes – would have to be exposed.

The next task after leaving Elsa was to explore Bullo Pill, which I had never seen. It was some four miles away and if I went there at once I should avoid the long tramp back to my den and out again. I expected an ugly jumble of decaying dumps and buildings, for I knew that it had once been a little port where barges loaded coal for transport across the river to Arlingham.

Reality was very different. When I passed under the railway bridge from farmland to the usual close-cropped meadow of Severn banks there was hardly a sign of industry but the two stone buttresses at the entrance to the pill, which was a valley of mud some thirty feet deep and as much across with the usual insignificant stream at the bottom. On the northern bank were a group of three cottages and a small factory beyond them.

The southern bank reminded me of an archaeological site where the turf has been replaced and only the lines of foundations can be detected. This Severnside lawn ran away for a quarter of a mile in even beauty bounded inland by a delicious avenue of great hawthorns, perhaps remains of a double hedge. Along the river front were stone bollards to which barges must have tied up while waiting for the tide. There could never have been room for more than three or four inside the pill.