P14 Eddystone Fatboy?

[Patrick Chadwick]

I don't believe the rifle has ever been out of her stock since the forward barrel chamber screw is still staked, I can't turn it.

Oh yes it has, as I mentioned previously. Take a careful look at the 5th/last photo in your 1st post. The stake mark should be right on the screw slot, the idea being to drive a bit of metal into the slot to lock the screw. A stake mark that is not on the slot will merely increase the turning friction a bit, but presents no problem to a well-fitted screwdriver, properly applied. The slot itself has been marred at a later date as a result of using a poorly fitting screwdriver to remove the screw - look at the burr on the left side of the slot, towards the stake mark. When the screw was tightened up, the slot then turned past the stake mark, as you can see in the photo. This is not surprising, as even the best matured wood will still shrink a tiny bit over a century!

"I can't turn it".
It may well have been overtightened on the previous re-assembly - look at the burr on the right side of the slot, away from the stake mark. A trigger guard screw should be tightened so that the wood still has some elasticity, not crushed to death!

If you want the best possible shooter, then it is anyway necessary to remove the barrelled system, clean everthing, and oil the stock with linseed oil on the INSIDE (not just the outside) - which is where the wood dries out more than anywhere else - make any bedding adjustments that are appropriate, and re-assemble the rifle, thereby tightening up the trigger guard screws to a torque that is correct for a stock that is now a century older than when it was first assembled. And like the wheel nuts on an automobile, you should check the torque after a few weeks (time) and a couple of dozen shots (stress) as the freshly oiled wood will also need to settle down.