The tlachtli player sprinted up the 300 steps to the apex of the ziggurat, displaying the fitness and fearlessness that had made him such a star of the ball court. To tumultuous applause from the onlookers, he threw himself flat on his back on the altar, all smiles. Naked save for a loincloth, he had ceremonially anointed himself beforehand with sweet-smelling oils. He offered his bare, glistening chest to the priest, who muttered ritual phrases over him, then took an obsidian-bladed dagger and raised it aloft.

With a practised, powerful stroke, the priest pierced the tlachtli player’s torso. Blood exploded from the wound, and the young man died with a scream and a shudder that were as much ecstasy as agony. The acolytes then hauled the body off the altar and set about hacking the ribcage open and sawing out the heart.

They placed the still-twitching organ in a large iron basin which sat on a tripod over a bellows-stoked fire. The heart sizzled and sent a wisp of smoke up to heaven. Meanwhile, the acolytes pitched the eviscerated corpse off the rear of the ziggurat. It tumbled into a fenced-off enclosure below, for later disposal.

The cooked heart was handed to the priest on a skewer. He took a bite, then tossed the remainder aside. He would do the same with every victim’s heart this afternoon, although the bites would become increasingly small until, by the end, they would be the tiniest nibbles. There was only so much meat one man’s stomach could handle in one go, and the human heart was a tough, tasteless morsel.

The next victims climbed the stairs, somewhat more slowly and reluctantly than the tlachtli player had, in a group.