Some Enfields have alot of cosmo and gunk in the FP channel, or worse have damaged firing pins and need to be removed. I've had to take a bunch of them out over the years.
I don't have pics of mine, but a VERY easy tool to make. Get a hollow-shafted 1/4" nut driver, then grind down the head of it so that it leaves 2 "teeth" at the 12 and 6 oclock position. You can look down into the bolt to see the notches it must engage (they are not perfectly square, btw).
If you get a FP that's really stuck in there good, attach vice grips to the shaft for some extra torque.