Legio I Italica

[Purplest]

why they would send a Centurion and subunits from this legio all the way from Dacia to north Britain?

Centurions were often detached from their legions and sent on special assignments elsewhere - they didn't necessarily take any men with them.

In this case we would need a building inscription or something left by the men of I Italica itself to prove that elements of the legion were in Britain. Otherwise it looks like Candidus was there by himself!

Two Antonine governors of Britain, Papirius Aelianus and Statius Priscus, had previously governed Dacia; it's plausible that centurion Candidus might have come to their attention during that earlier command, and his skills in engineering or construction supervision later led to his brief transfer to Britain. It was presumably intended to be temporary, as otherwise he would probably have been appointed centurion of one of the legions based in Britain itself.

Mr. Ross,

What you say makes a lot of sense. As along Hadrian's Wall there are a number of inscriptions left by the legions which built it. But Hadrian's Wall was actually a wall with forts, etc. and wasn't the Antonine Wall mostly earth works? There may not have been as many places to leave inscriptions by the legions. In the light of this there probably isn't as much physical evidence to be found compared to Hadrian's Wall. Also, the Antonine Wall wasn't used but for about 20 years before it was abandoned. 

Cheers,
Thomas