It makes no sense

[Mark Hygate]

What is a bit strange is why did the Roman engineers bring Hadrian's Wall all the way down from its high vantage point of about a mile above the top of the Tyne valley at only this place where there was a bridge over the river,.....................

You're definitely not happy with the fact that it doesn't seem to connect to the wall.

Me, however, as I've suggested - the fact that it doesn't makes perfect sense. Your points that the wall deviates particularly at this point; the fact that this is a strategic crossing point; and, most likely indeed, that the crossing point and the need for a defence and a garrison on troops to provide that defence pre-dated the wall at this point are all suggestive to me of supporting my reasoning.

As Brian mentioned, Newcastle castle was built right on top of the fort site, so determining the exact plan and layout is difficult. As far as I know, the only internal structures to have been discovered are a bit of the praetorium floor and part of one of the granaries. .....................
I would think that forts of any size would have workshops or stores - any group of soldiers is going to need to repair equipment, slaughter animals, brew beer, store clothes and foodstuffs, mend boots and so on, and there's only limited space in the barracks for that...

Thanks for the additional background.

I would, however, argue that whilst storage of bulk grains to provide a significant store of food is part of the logistic supply of the garrison(s) in that vicinity and meets with the grain storage we seem to find in most forts (of any size); none of the other things need to be carried out within the defensive perimiter of the walls.

The garrison's own money, personal effects, the records, the Prefects/Tribunes house and chattels and said personal clothing and equipment; let alone the graneries and more than enough space for stored water would indeed be inside the walls.

But the: repair of equipment; slaughtering of animals; brewing of beer; etc don't need to be within the walls and are much more likely in the major vicus that would have grown up around this most important settlement area - hence why it's also now Newcastle. :wink:

This, IMHO, is not a 'castle' that is there to withstand a siege - it is a significant fortlet placed to survive long enough for reinforcements to appear; whilst acting as a firm base to control and supervise movement across the bridge, up and down the river and across the wall.

Personally I'd plump for a large cohort.