Children of the Stones was produced by HTV and is owned by Acorn Media.

Avebury was produced by neolithic peoples and is owned by English Heritage.

Anything else is subject to plausible denial.

The druid prince stood on the wooden platform that marked the focal point of the stone circle that would someday be known as Avebury. He had performed this ceremony many times, according to the ancient formula set long before his people ever came to this wind-and-rain-swept land. That was not what bothered him.

The crowds milled around the edge of the circle, expectant, as the chosen participants gathered to form a human circle around the platform. Their mutterings and occasional cursing reached the old man as he prepared the final part of the fortnight-long ritual. This, too, was not what bothered him. He'd long-since learned to filter out human voices.

The bright star, where once a dim star had been. That had given him some concern. Particularly because, now the bright star had faded away, the dim star that had been there was nowhere to be seen. How does one perform a ritual to a star that wasn't? The death of chief druid Dai, at the hands of others, on the day the bright star vanished - that too unnerved him even though Dai was against performing the ritual. However, the stars will do what they will and violence was a way of life for the Iron Age people who had settled here.

No, even these were not what really disturbed him, he decided. It was the reversal in the flow of energy. Where once energy flowed down from the star, through the circle and out into the land, he sensed that energy was now being leached away. The ritual, which converted the stone circle into a gigantic powerhouse, was not going to behave as it once had. What would happen was now anyone's guess, but the ritual had to go on. The formula was quite specific on that point. No matter what, the ritual had to happen.

Besides, he would still be rejuvenated and reinvigorated. It didn't matter if the energy flowed uphill or down, just so long as it flowed through him. He knew that much at least. Admittedly, the Druid council of Anglesey had urged against it, and they had threatened to take action if he continued with the ritual, but they had never felt this strange power and so had never faced life with the prospect of being denied it.

The time approached. The moment was almost at hand. The song the formula required, if song it was, was being delivered by the chosen. The circle was complete. He raised his eyes and hands to the heavens, unaware that two of the chosen - under orders from the Druid council - had broken that circle. The energy blazed around him. Too late, he saw his danger, the imbalance created by the ones who broke rank. The energy escaped his control, twisting, coiling, wrapping round the singers below.

The two fled, as he burned in the mystical fire. His final thoughts were that there was no sanctuary that could escape such as this. Then the energy consumed the structure of time itself and he thought nothing more.

Time was now itself twisting, the bringing of the Outsiders and the tragedy of the ritual burned into it. It was time, not a given individual, that was rejuvenated. Laid out on top of the reality outside of the circle complex, the events would replay over successive generations, trapping the instability and preventing the energies involved leeching spacewards until the world died.

The Druid council studied this instability and devised a new formula. With the Druid destroyed and the two chosen escaped, the spiralling morass of time would need two Outsiders for each time the ritual was to be performed. These would need to be selected carefully, to prevent the success of each new Druid. Just the right information would have to be given at just the right points in time, with just the right incentives.

Chief Druid Dai and the Druid Prince would reform from time itself. Reborn before they died, a Celtic knot that folds under itself. Drawn in because the knot always loops back on itself.

But two singers had fallen, when the instabilities rippled outwards, and had not become part of the loop. Each loop would cost two different singers, but this would now always happen. They, too, would need to be replaced by Outsiders, chosen specifically to be able to remain in the village and not suffer.

This new formula, they realized, must survive no matter what. They expected that someday they, too, would be replaced the way they had replaced those before them. Traditions would need to be devised, rituals ingrained, so as to ensure the preservation of the pattern for as long as it was needed, for as long as the time twister remained.