Then, when it seemed that the chant could not get any louder, the high priest bent and rose up with a narrow-bladed dagger clutched in both hands. He raised it slowly and the polished steel of the blade reflected the glitter of the flames. All eyes were fixed on the spectacle being played out at the altar. Cato glanced at Macro and saw the clenched jaw and his left hand tightly clutching his right fist as if to stop it creeping towards the handle of his sword. As Cato’s eyes turned back towards the altar, the chanting stopped abruptly, as if the breath had been torn from the lungs of every one of the natives at precisely the same instant. The silence was as awe-inspiring as the sound had been a moment before and there was only the soft distant rustle of a light breeze and the faint crackle of the fires.

With a shrill, inhuman scream the High Druid stabbed his blade down with all his savage strength. The point plunged into the white tunic over the boy’s heart with such force that his arms and legs jerked wildly and the air exploded from his lungs with a half cry, half grunt. Then his head snapped back, jaw agape as he screamed briefly and writhed beneath the dagger that pinned him to the altar. The blood quickly soaked through the cloth and pooled on the stone surface before a dark stain began to trickle over the edge and streak down the side of the altar. Then the boy was still and the natives whispered a sibilant sound to mark his death. ‘Sa . . . sa . . . sa.’

‘Sick bastards,’ Macro groaned through his teeth. ‘Sick, savage fucks.’

Cato hissed a warning. As the people round the ring looked on, the High Druid set to work with his knife, opening up the dead boy’s chest, and Cato could see wisps of steam curling into the chilly air. Then the Druid leaned forward and dipped a hand in and wrenched out a bloody lump of flesh and examined it closely. The boy’s heart, Cato realised, and his throat tightened with nausea. After a lengthy delay, the Druid lowered the organ and looked round his audience before he made an announcement. There was an audible sigh of relief from the tribespeople.

‘The High Druid says that the heart is good and strong and will make a fine offering to the gods,’ Marcommius explained to the Romans in a hushed voice. The Druid turned to a small brazier burning close by the altar and tossed the heart into the flames. The fire instantly flared brightly and a large cloud of smoke billowed into the night sky. Some sleight of hand, Cato reasoned. The Druid had somehow thrown something in with the heart. Still, the effect was impressive and certainly had an impact on the audience who had instinctively flinched at the brief burst of light. Then he realised that the High Druid had disappeared at the same time, just as if the ground had swallowed him up. There was an anxious muttering before the Druid who had escorted the Romans and Iceni to the rings stepped forward and raised his hands to quiet the crowd.