The Bunker Group
Verified Defense Pro
Having worked on T23 / T45 & visited with T22 / T42 on occasion, the RED arrow is indeed pointing at the hoist for taking the 4.5" inch shells (in their containers), down into the deep magazine.I readily admit this is a guess on my part, but I would think that the hatch pointed out with the red arrow, the one which has the message about a hoist, might very well be an access hatch and hoist to reload the magazine for the gun. It would be interesting to see if vessels in service with other navies have similarly looking hatches in approximately the same location behind the main gun. Or perhaps one of the DT members who actually work with ship designs or in construction might be able to chime in.
In your discussion you also mention the 'Escutcheon' plate. That is quite literally the 'cover' that can be secured in place, to 'block up' the hole where the key goes into the locking arrangement for the door on the top of the hatch. It is there purely to seal the hatch trunk, & prevent any sea water getting into the trunk under heavy seas.