More years ago than I care to count, and before things ached when I walked, a friend had a No.5, imported during the 1950's. He had removed the flash hider. I was even, if possible, more ignorant on guns than I am now, and I thought the flash hider was to hide the muzzle flash from the enemy to prevent disclosing the shooter's position.
We were firing that rifle late in the afternoon and after a break decided to fire a few more shots, even though by that time we could barely see the target. Firing Mk VII ammo out of that short barrel in the near dark was an education. Each shot produced a bloom of red, violet, orange, and yellow flame about 3 ft. in diameter and 5 ft. long. When I fired my shots (2), I couldn't see for several minutes. That coupled with the blast (our ear protection was sadly inadequate) left me helpless. An enemy armored division could have come up on me and I would have been unaware of them. So a No. 5 taught me that the primary purpose of a flash hider is to hide the flash from the shooter, not from the enemy.