At the start of Time’s Chariot, time travel has been possible for the last four centuries and will continue to be so for the next 27 years. Not everyone is happy with this.
Jean Morbern conducted his experiments at his secluded base in Antarctica, and by pure chance he discovered how time travel could be possible. He made several ill-advised excursions through time himself, and was horrified to discover that in doing so he had created several different timelines; different versions of history, and hence several billion more people than would otherwise have existed. He was effectively playing God. It played fast and loose with the structure of the universe and the easiest way of undoing the damage would be to uncreate them. But Morbern wasn’t going to murder billions of innocent people.

Morbern therefore founded the College of Advanced Manipulation of Probability and Chronotic Transference. The College would safeguard the timelines, and make sure that no more were created. The timeline that Morbern knew, the “official” version of history, was named the alpha stream; the others were named beta, gamma and so on. Operatives from the College would go back in time to the early history of the other timelines and begin to infiltrate them; by their version of the twenty sixth century, they would be entirely governed by the College. They would then be spliced back into the alpha stream. The balance of the universe would be restored, and no one would be edited out of existence.

Morbern knew that his singularity would collapse into nothingness after about 400 years, and time travel would no longer be possible. He had no intention of letting anyone else use the kind of power he had inadvertently tapped; he therefore destroyed all records of his research and put the College’s operations under control of an artificial intelligence known as the Register. The Register governs all travel through time, and makes sure that Morbern’s Code is enforced. It will self-delete when the singularity collapses, time travel is no longer needed and the College becomes redundant — in 27 years time.