‘Thank Taranis,’ Vindex said.

Ferox glanced up and saw a line of auxiliary archers. Behind them Arrian, still on horseback, gave him a thumbs up. He hoped the tribune would not regret making himself such a tempting target.

One of the hand-held engines cracked like a whip as it shot. The sound was higher pitched than the bigger engines, but still spoke of formidable power. Another pikeman fell, then another and a third as the man he was loading for shot. Arrows slammed into them as Arrian must have ordered some of his men to switch target.

The phalanx broke. Men at the front, helpless against the shots coming from the side, dropped their sarissae and turned, trying to run. The men at the back hesitated, unsure, and did not begin to flee for a long moment.

‘Kill the bastards!’ the princeps posterior yelled at his men and led them on, bounding over the mass of fallen pikes to drive his gladius into the back of a man with feathers on either side of his helmet.

‘Kill them!’ There was an animal quality about the roar as the men of the first cohort surged forward. Confused, packed together on the bridge, the pikemen were helpless. Some men thrust, but most cut and slashed, the drill book forgotten as they hacked, fear and anger blending into rage. The sound was like a crowd of butchers chopping meat, and men were covered with blood.

‘Prisoners!’ Arrian shouted at them. ‘We want prisoners!’

Only the legionaries at the rear of the column listened, and they could do nothing.

‘Bastards! Bastards!’ a legionary grunted each time he cut.

‘We want prisoners!’ Crispinus had ridden up.

‘Bastards!’ Another pikeman fell, this one with his neck almost cut through. Men slipped in pools of blood and tripped over the corpses or moaning wounded. Half the phalanx died before the press relaxed and the rest fled. Shooting from the walls redoubled. A stone, twice as large as the others, skimmed across the bridge, killing or maiming a dozen Romans.

‘We’re going!’ Ferox called to Vindex.

‘Bout time.’

‘Back, lads, that way!’ Ferox pointed to the path they had followed down. Holding the sack with one hand, he scooped up his shield to cover them. Vindex came to stand on one side and Bran on the other.

‘Shit!’ Vindex spat out the word as an arrowhead burst through the back of his shield before stopping. He glanced past the edge to stare up at the walls. ‘Let’s go home!’

‘Wish we could,’ Bran said.

A stone, one thrown by hand or sling, banged on the front of Ferox’s shield.

‘You can go, if you like,’ Ferox told Bran.

‘No I can’t. Not until you two go.’

‘We really are humped, aren’t we?’ Vindex said.

Ferox peered back over his shoulder. His men were all up. ‘Slowly back,’ he said. They took one step, then another. Dirt flicked up onto Ferox’s foot as another stone just missed. ‘Right, run for it!’ All three men turned and fled, and happily their archers shot another volley at that moment, which helped them all scramble up the bank and reach safety.