A horn blew, faint and distant, followed after a moment by the rasp of a cornu, much closer and louder.

‘East gate,’ Ferox said, as much to himself as anything else. ‘Excuse me.’ He loped past Lepidina to the back of the tower and shouted down. ‘Sound the alarm!’

The three tubicines on the level below had already spat to moisten their lips and now raised the long trumpets and started the fanfare ending in a peal of three notes, repeated again and again.

‘That’s enough!’ Ferox called down. He could see movement around the nearest barracks as men ran out. Anyone who had not woken by now was unlikely to be roused by more blasts and he wanted to be able to hear any signals from the rest of the fort. Down below a horse was waiting in case he needed it to get quickly from one side of the fort to the other. There were no more trumpet calls, nor sound of ox horns from outside, and the only shouts came as the woken men were formed up. On the ramparts and towers – at least to the little distance he could see – everyone was alert and expectant, staring out into the mist. There was no sign of any threat here, and no noise of heavy fighting from the east gate.

The gates were the weak spots as was bound to be the case. If this was a full assault with rams and other engines, then it was easier to knock down a gate than a section of timber and turf rampart. More likely, the enemy would hope to rush the fort and bring nothing more sophisticated than ladders and ropes, but even so they would attack near the gates because only in front of these were there easy paths through the obstacles and over the ditches. The porta praetoria was the most vulnerable of all, for even without this mist the houses of the canabae gave any attacker plenty of hiding places at night.

‘I suppose that I had better go,’ Lepidina said. ‘And get all the slaves to shelter so that we are not in your way.’ If she was nervous then there was no trace of it in her voice or manner.

‘It would be best, lady,’ Ferox said. ‘But thank you for the food.’

Ferox was itching to run to the east gate, but that was not his job, not yet at least, and he had to stay here and wait for reports. This was where he had told all the officers that he would be and they all had instructions. In the intervallum behind him, some thirty men had formed in six ranks as reserve under an optio from I Minervia. Similar parties were ordered to wait at intervals around the fort, while Tiberius Claudius Maximus ought to be getting all the remaining mounted men in the garrison ready to ride at a moment’s notice. Their station was outside the principia, for the horses had been kept in its courtyard, which would no doubt need thorough cleaning when all this was over, at least if anyone was left to do fatigues.