Batavians: an offshoot of the Germanic Chatti, who fled after a period of civil war, the Batavians settled on what the Romans called the Rhine island in modern Netherlands. Famous as warriors, their only obligation to the empire was to provide soldiers to serve in Batavian units of the auxilia. Writing around the time of our story, the historian Tacitus described them as ‘like armour and weapons - only used in war’.

Berytus: the modern city of Beirut, had been refounded as a colony for Roman army veterans. Their descendants provided many recruits for the legions.

Brigantes: a large tribe or group of tribes occupying much of what would become northern England. Several sub-groups are known, including the Textoverdi and Carvetii (whose name may mean ‘stag people’).

burgus: a small outpost manned by detached troops rather than a formal unit.

caligae: hobnailed boots worn by soldiers.

canabae: the civilian settlements which rapidly grew up outside almost every Roman fort. The community had no formal status and was probably under military jurisdiction.

carrobalista: a light bolt-shooting catapult or scorpio mounted on a cart.

centurion: a grade of officer rather than a specific rank, each legion had some sixty centurions, while each auxiliary cohort had between six and ten. They were highly educated men and were often given posts of great responsibility. While a minority were commissioned after service in the ranks, most were directly commissioned or served only as junior officers before reaching the centurionate.

centurio regionarius: a post attested in the Vindolanda tablets, as well as elsewhere in Britain and other provinces. They appear to have been officers on detached service placed in control of an area. A large body of evidence from Egypt shows them dealing with criminal investigations as well as military and administrative tasks.

cataphract: a cavalryman who wore heavy armour, protecting arms and legs as well as body. Some had helmets with masks to cover their faces. Usually, the horse was also armoured. The primary weapon was the two-handed kontos or lance, backed by a sword. Some may also have carried bows. Parthian cataphracts were famous and combined with the more numerous horse archers proved formidable in open battle.

clarissima femina: literally ‘most distinguished woman’, this was an honorific for a female member of the senatorial class.

cohort: the principal tactical unit of the legions. The first cohort consisted of 800 men in five double-strength centuries, while cohorts two to ten were composed of 480 men in six centuries of 80. Auxiliaries were either formed in milliary cohorts of 800 or more often quingeniary cohorts of 480. Cohortes equitatae or mixed cohorts added 240 and 120 horsemen respectively. These troopers were paid less and given less-expensive mounts than the cavalry of the alae.

commilito (pl. commilitones): literally ‘fellow soldier’ or ‘comrade’, this was a familiar form of address used most often by men of similar rank. However, Julius Caesar was noted for addressing his men in this way. Most emperors felt it was too familiar and did not use it, but some – and probably some senior officers – did.