Enough of Elsa for the moment – though I can never have enough. We returned in time for the hour of meditation, which out of courtesy to my hosts I attended. For me meditation is more peaceful and productive after half a litre of claret and a square meal, but on this occasion I had plenty to meditate about: whether I could save myself from falling desperately in love with Elsa and how much to believe of the story of the win on the pools. It neatly accounted for the comfort of Broom Lodge, which had puzzled me, as well as for the unproductive farming and the impossibility of any large profits on Marrin’s buying and selling of gold; all the same, he was not the sort of character to study football results and to waste time and money on a weekly gamble. Of course he might have done it once only and produced a winning line by following some incredibly effective cabalistic formula, but a pious and profitable burglary for the sake of the commune was far more likely.

By the time the party broke up with a monotonous chant my thoughts had switched to salmon fishing, Marrin’s early and wildly imaginative scheme to raise some cash. Since I myself am a competent skin-diver, I was eager to talk to him about the risks of the Severn Sea and the possibilities of underwater exploration.

First I engaged the major in conversation on the founding of the colony, so that there could be no reason to suspect Elsa of giving the story away. He avoided any discussion of the win on the pools, saying that there were many unexpected ways in which the spiritually minded could be rewarded. When I suggested that the acquisition of worldly wealth was usually supposed to distract the Soul from the Way, he did not agree. Poverty was desirable for the monk but not for the monastery. This led quite naturally to the early skin-diving for profit. Later on, the major said, it had become a rite. Marrin’s secret swimming with the fish was symbolic of the unity of life.

Symbolic, hell! A typically woolly explanation! I had little doubt that Marrin would not shrink from fraud in propagating his gospel, but in his beliefs he was sincere. As I lie here in the discomfort and physical content of any primitive pagan, his doctrines seem as absurd as those of the more fantastic Christian sects. Yet one must remember that, to a pious lama, Broom Lodgism might seem more or less acceptable except for its emphasis on service to mankind rather than the perfecting of the soul. But that is irrelevant. The dynamic energy of a religion derives from belief, not what is believed.

The subject came up naturally when I was discussing with Marrin the horseshoe bend of the river and the Severn bore which begins there, racing up ahead of the tide like any ocean wave and leaving a full estuary behind it.

‘I think I am the only person to have explored the bed,’ he said, ‘and at such a depth that I could let the bore pass over me.’

I remarked in all innocence that I wished I could dive with him – but at slack water, thank you very much! He replied at once and cordially that I mustn’t hope to catch salmon. I would do better to come down to the Forest next season and learn to use a lave net, spotting my salmon as it drove upstream and racing along a sandbank to intercept it.

‘They always swim close to the surface,’ he told me. ‘That was where I went wrong. I had a theory that they would swim deeper where they could. So I tried the deep pools where the main channel passes close to the shore. It didn’t work, but it was a great joy to rest on the bottom and watch the fish passing overhead when the water was clear enough to see the streak of silver.’

‘But why do you go out at night?’

He hesitated, his enthusiasm gone. ‘Because I found that at night I could feel as a fish feels. In the light one is only a man swimming. That is your answer!’

We were both silent for a moment; but then, apparently realising that he had been too abrupt, he asked, ‘What has been your experience underwater, Mr Colet?’

My interest had not been in fish, but in the remains of historic ports where little remained to be seen on land – like Tyre, I said, reminding him of the quantity surveyor. Also I had accompanied a small party of pre-historians who maintained that if you wanted to study the palaeolithic you must not be content with cave dwellings by inland streams but must dive for caves now covered by the sea.

I explained that in the last ice age when sea levels were lower than at present, river levels must also have been lower. For example, the mouth of the Severn must have been somewhere down the Bristol Channel between woods and marshes that were now shoals; and the wide valley, where the ebb and flow of the powerful tides now played merry hell with channels and the banks, then contained a clear river of fresh water fed by the glaciers of the Welsh mountains.

‘I have seen no such caves. Where would they be?’

‘Beneath the ledges where Severn cliffs once stood before they were eaten back.’

‘All crumbled away, Mr Colet, crumbled away to mud and sand, Severn has no cliffs underwater.’

‘I think that here and there you might find a clean edge scoured by the tide if you looked at the bottom of the ebb.’

‘Pardon me, Mr Colet, but you are wrong!’ he exclaimed. ‘No sheer cliff exists.’

He reminded me of one of my old tutors who, when contradicted however politely, would lean towards me with chest thrust forward and head back, seeming to take up an S-curve like a snake about to strike. I assumed that Marrin had visualised package tours of pre-historians or geologists come to disturb his communings with the salmon. It was from that point, I am sure, that he began to wish that I had never called in at Broom Lodge with my awkward curiosity. It was not my fault, for he had encouraged me both to ask questions and to answer them. Ancient economies interested him from two different points of view: religious doom-watching and subsistence agriculture.

Our conversation left me with a feeling that Marrin considered the Severn his private property from which trespassers must be warned off. Such jealousy was quite natural; the mystical side of his night dives could be enough to account for it. But the solvency of Broom Lodge continued to puzzle me. Somewhere there was deliberate deception. I had an impression – which I admitted might be due merely to his skeletons of sea creatures – that the thread of gold seemed to run out of the laboratory into the Severn and back again.

At the next chance of a private talk with Elsa I asked if her uncle had made a serious study of alchemy.

‘From books, yes,’ she replied, ‘and I know he used to muck about with experiments in the old days. But of course he didn’t have a proper laboratory of his own till he could afford to build one here.’

To my astonishment, Elsa, who was so scornful of the beliefs of Broom Lodge, had been impressed by the paraphernalia of alchemy and did not rule out the transmutation of metals. She was in good company. Isaac Newton had believed it possible and in later life suffered from fits of insanity, probably due to the ingestion of lead and mercury which he lavished on his experiments.

‘Then you don’t believe the football pools story?’

‘Do you?’

‘Well, it’s possible.’

‘That’s what I feel about the gold.’

I objected that it was not possible. Gold could be made from lead but required immense and uneconomic plant – lasers and cyclotrons and God knows what. It couldn’t be made by a rack of crucibles and a magic circle.

‘But don’t ask him about it,’ she warned me. ‘We talk of it ourselves, but never to him.’

I decided that gold was none of my business; it kept this hospitable colony happy and prosperous, and the profit and loss account was a matter for the Inspector of Inland Revenue, not for me. So my thoughts returned to the trade balance of Roman Britain and its commerce. This, the original object of my wanderings, had rather faded away – not unnaturally, considering the excitement of Elsa and the surprising efficiency of Broom Lodge in spite of being collectively devoted to poppycock.