While he thrashed at the material with his legs, Cato used his spare hand to try to pull the toga away from the Emperor’s body. The wool was like a live thing, squirming in the chaotic current, the folds wrapping around Cato’s hand and arm. With one last pull it came off and both men came up, heads and shoulders clear of the water as they gripped the branch. The water around them was no longer raging quite so much and Cato could see for the first time that they had been swept some distance from the end of the vale. Around them were the remains of the tables, and Cato saw Tigellinus, some fifty feet away, trying to haul himself on to one of the table tops, which was spinning round in the fast current.

‘Cato!’

He turned and saw a commotion in the water where Macro was trying to swim towards the branch. Then, between them, another figure came up coughing and hacking, his arms flailing to keep him above water. Cato saw that it was Tribune Burrus.

‘Over here, sir! Here!’ Cato waved his arm and Burrus began to kick out towards him. The tribune reached the branch and wrapped his arms over it, gasping for breath. Cato looked round and saw that Macro would join them in a moment. Then he noticed something strange a short distance ahead of them. The leading edge of the wave just seemed to have disappeared, leaving a sharp line no more than fifty feet away.

‘Oh shit,’ Cato muttered. ‘The river …’

The tree, and the men clinging to it, were being swept towards the steep riverbank and down into the river. Cato put his arm round the Emperor and clung tightly to the branch. He saw that Macro had grasped the end of a smaller branch a short distance away. Cato filled his lungs and cried out above the din of the rushing water, ‘Hold on tight! We’re going into the river!’

The end of the branch abruptly shot out into thin air for an instant. Then it tipped over the edge. Once again water closed over Cato and he felt his legs being scraped by rocks and debris as the branch dragged those hanging on to it under the raging surface of the river. The water roared in Cato’s ears and his lungs began to burn. The Emperor seemed to writhe against him, but it was impossible to tell if he was struggling or simply being battered about by the current. Then there was a swirl in the water and the branch broke the surface. Cato snatched a deep breath.

‘Sire, are you all right? Sire!’

The Emperor retched and spluttered and rested his head on the branch as his body was wracked by a coughing fit.