The Roman forts in Britain were usually built by the Legions. But evidence from an inscribed dedication slab on a granary building at Benwell (Condercum) states that the men of the British Navy built this. Roman marines were famed for their specialist engineering skills - which they brought to bear in Roman Newcastle for the Emperor Hadrian.
The slab was thus: IMP CAES TRAIANO HADRIAN AVG A PLATORIO NEPOTE LEG AVG PR P VEXILLATO CLASSIS BRITAN
In English: For Imperator Caesar Trajanus Hadrianus Augustus, [under the administration of] Aulus Platorius Nepos the pro-praetorian legate of the emperor, a detachment of the British Fleet [made this].