This was only part of the great projects undertaken to help the army secure the region, and the last to be completed. For several years now barges were able to bypass the long stretch of rapids on the Danube by using the new canal, aided by the road which for miles ran along the river, often cut out of the living rock. All of that had been completed while Hadrian was last in the area some three years ago, when the bridge was little more than plans and a bold idea. Now, it was almost finished, conceived by genius and turned into stone and timber reality by the labour of many soldiers, including the contingent from Legio I Minervia.

It was natural for a commander to take an interest in work done by his troops, and equally natural that when officers visited the site they asked the presiding architect about the project. Hadrian had put great thought into his questions, wishing to demonstrate that he was no ignorant aristocrat, showing interest for form’s sake and caring little for the answers. So he had asked about the details of the design, of the forces in play, of weight of material and current. They were good questions, useful questions, but Apollodorus’ answers were the same vague platitudes designed for the ignorant. Hadrian pressed him, trying to show that he was different, and even anticipated part of the answer in his question.

‘Apelles to Alexander,’ the architect had told Hadrian, not bothering to explain the allusion. Piso, who had up to this point shown no deep interest, sniffed as if he understood.

Hadrian struggled to control his anger, aware that his face had reddened. It was an old story, and like so many about Alexander the Great, hard to know whether or not it was true. While sitting for a portrait at Ephesus, the Macedonian king had chattered away to the artist and his assistants, asking about composition and colours, and often making suggestions. Eventually Apelles, already famous and soon to win even greater reputation when Alexander declared that only he would be allowed to paint the royal image, told the king to stop talking, because even the lowest apprentices were laughing at his ignorance. The rebuke was a sharp one, arrogant because for all his great skill Apollodorus was speaking to a vir clarissimus, a member of the Senate, let alone kin to the princeps. It was also unfair, for engineering and architecture were among Hadrian’s great passions, and his interest was as informed as it was genuine. He would let the Syrian have his moment, but still wanted to learn all that he could. So he had asked to see some of the plans and said that he wished to take a tour around the bridge from the river. Apollodorus had agreed – it would have been hard to refuse – and delegated this underling to the job.

Ephippus was a Greek from Syracuse in Sicily, who stuttered and twitched in the presence of the distinguished guests, but tried his best. His nervousness was not helped when Hadrian requested that an engineer come with him on his tour of the garrisons to provide technical advice, prompting Apollodorus to say in front of the Sicilian that he was sure he could spare him. By now Hadrian was satisfied with the choice. He had been patient with Ephippus, encouraged him with his smile and by gradually moving from simple to complex matters as he asked about the bridge. The man struck him as thoroughly competent, with extensive knowledge, if lacking in the spark of inspiration or any real appreciation of the aesthetic as more than just theory.