Marvellous! That was all I needed for my diversion. It was the robe I had set on fire which at once put the idea into my head. I smashed the lamp and laid one of the torches by its side. On that foundation I built a bonfire of the cases, the robe and the coats, lit the second torch and threw it on.

Smoke poured out of the recess and up the gallery towards the entrance. I hoped that would happen, for it would bring down the alarmed picket at the top, while leaving the air of the cavern clear for the present; but I had not reckoned on such a volume of fog in a confined space. We should all have been asphyxiated if my old friend Nodens had not overruled his son and sent flame from heaven to lessen the smoke.

The party from the top came rushing down and entered the cavity coughing and choking. I was outside it, a little distance down the gallery and safe from detection. Holding my wet shirt over my face, I tip-toed past the changing room and ran for the entrance which seemed to be acting as a chimney. When I had passed it there was little more than haze – for which I thanked God since I had a vision of Elsa and Denzil trapped in their dead end.

I called to them to run towards me and to hold their breath as they dragged themselves out to the open air. Elsa went first while I held the golden cauldron. The major was more alarmed for that than for her, so I handed it over to him and told him to hurry. When I myself reached the surface I had a longish bout of coughing and spitting before I could speak at all. I could only touch Elsa’s hand before I threw myself at the job of replacing the pit props.

‘We must not close them up,’ the major protested.

‘My God, we must! How do you think that Elsa can face any of them and what lies they are going to tell the commune? Leave them here for a day or two while we think!’

Elsa helped me. The major decided to let Arthurian chivalry go to hell and lent an efficient hand. The Grail, which had escaped with only a slight dent below the rim, sat on the grass and watched us.

‘But how?’ I asked her.

‘Well, I knew they wanted that bloody bowl more than anything else, so when you didn’t turn up I thought I’d swop it for you, and for Denzil of course. You had described the place so exactly for me. I got lost all the same and was nearly going to give up when I saw the Broom Lodge van standing on the track. Then I found the old gate to the workings and followed the foot of the slope till I saw the hole wide open.’

‘But light?’

‘Piers, darling, I am grown up! I brought a torch and then chucked it away as soon as I could see down into the cavern. I thought it would spoil my entry if I didn’t use both hands to carry the bowl. Scene Three. Priestess rescues lover. Tripey plot by Verdi and music by Stravinsky.’

She began to sob with relief and I held her close.

‘What do we do now?’ she cried. ‘I can’t go back to Broom Lodge, and you’re icy and shivering.’

‘Stick your robe on him!’ the major ordered. ‘And you can have my anorak.’

The dark green anorak and her brown tights suited her very well. She reminded me of the principal boy in a pantomime. I did not say so. I was so glad that she belonged again to our sanctuary of the trees, and not to the altar of black waters. As for me, I tied my wet clothes up in a bundle and put on that fragrant robe. The warmth of her body and her laughter when the shoulder seams split restored me.

‘Where are we to go?’ she asked. ‘No hotel would take us.’

I said that I could offer some Robin-Hood hospitality for the night and that next day we would go to London. Meanwhile she should return to Broom Lodge, pack a case of necessaries and her smartest summer frock and slip out again on foot without being noticed.

She had boldly parked her car – snatched from the communal garage – on the track used by the ‘geologists’, and she drove us to the village of Wigpool where I picked up mine. We then made for Broom Lodge, she to the garage and her room, and I to the quiet forest road where I waited for her return.

‘Going to the British Museum, Piers?’ the major asked.

‘Yes, just as we intended before the burglary.’

‘May I come with you?’

‘Of course. Whatever Elsa’s bowl is, you are its guardian for the present.’

He did not object to my calling it Elsa’s bowl. Since, strictly speaking, it belonged to the commune, I thought he might object and so added the bit about the guardian.

‘I have not been found worthy,’ he said. ‘She has.’

I wasn’t going to tell him how the Grail had come into her possession and I doubt if he wanted any prosaic explanation of the mystery. For him it may have been the eternal destiny, or a reward for her selfless gallantry.

Elsa returned out of the night, transformed from priestess via principal boy to neatly dressed tourist, hair now primly plaited and coiled. I drove to the glade beneath my gloomy hill where sometimes I left my car and led them up to the den.

‘So this is the hotel where you lived!’ she exclaimed.

‘It is as it should be,’ the major said, reverently laying down the cauldron on the stump which I used as a table. ‘The vision of the angels and the forest hut.’

He must have been referring to one of the Grail legends in which the seeker was led to a humble hut full of light and music. Presumably it was also full of heavenly warmth, which my den was not. As the smoke could not be seen by night I lit a fire in the ruined hearth, and when I had changed to the gent’s suiting of Personality No. 1 we sat round the blaze till the sky behind the line of the Cots-wolds, far away across the Severn and its meadows, showed the grey of dawn. My own forest angel slept with her head on my lap.

I put out the fire and rolled the major’s blessed car rug round the cauldron, tying it up safely. Dawn and the presence of Elsa and Denzil, one representing the joyous spirit of earth and the other the mysteries of the wandering soul, brought on a moment of adoration. Suppose, I said to myself, I really have got, here rolled up in a rug, the Grail itself or that paragon of beauty which created the myth.

We drove into Gloucester and took the first train up to town. I expected the major to stay at my flat. I had only two bedrooms, but there was no need for embarrassment – by this time he knew very well what were the relations between Elsa and myself. He surprised me by saying that he would go to his club; a clothes brush was all he needed, and the valet would supply everything else. Clubs and valets seemed utterly out of character. But why should they? No doubt he wasn’t the only eccentric retired officer who turned up fresh from a religious meeting in some obscure and holy Himalayan village, or from a study of voodoo in the groves of Haiti, with nothing but an expensive suit of indestructible tweed.

‘No connections half as good as yours, old boy,’ he said, ‘but if Tony is there for lunch I could mention the Museum to him.’

I asked who Tony was.

‘Sir Anthony Aslington. On some board or other which runs the place.’

Aslington was only a name of power to me. There was hardly a national museum of art or antiquities in which he was not chairman of some committee. The best authority I could reach myself was the curator of the Middle Eastern Department.

‘And meanwhile you’d better take care of the bowl. Can’t allow it to be unpacked by anyone. Can’t leave it with the porter.’

It was curious how the Guardian could become outwardly the ex-officer of the Horse Guards. With no apparent stress he left behind the lanced and unstirruped cavalry of Arthur and returned to a world in which the plumes and armour of everyday were real.

‘You do the talking when we get to the Museum,’ he added. ‘Never was any good at lies!’

Once at home, I managed to make an appointment with my friend, the curator, for next day. Later he telephoned me to change the time as Sir Anthony wanted to be present. What the hell had I got hold of, he asked, that could interest that old sinner? I replied that I didn’t know what I’d got but hoped that one of them could tell me, and left it at that.