Although this would seem logical I point to my post earlier post which had five round in the cylinder and the hammer on a loaded round. If the hammer was moved the cylinder would rotate and fall on an empty chamber.
I'll point to my own earlier post where I said that most if not all revolvers by then had some sort of automatic safety which would prevent the hammer from reaching the primer unless the trigger was pulled.
Very early revolvers relied just on a half-cock, in which case resting the hammer on an empty chamber was a not uncommon safety precaution in case the pistol was dropped and the hammer was bounced off the half-cock. Some fairly early ones had features such as a hammer notch half way between chambers, where you rotated the cylinder to the half-index position lowered the hammer down into the notch to render it safe. Cocking the hammer would complete rotating the cylinder to line up a chamber with the hammer, ready to fire.
It didn't take long however for various trigger operated safeties to be developed such that the hammer can't reach the primer unless the trigger is pulled. A mechanism has to be either pulled out of the way or moved into the way for that to happen, and this is done by the trigger independently of the hammer. I don't know how the Webley or Enfield mechanism worked, but I would be astonished if they didn't have one of these types of safety systems in them.
Modern automatic pistols like the Glock accomplish what is effectively the same thing in another way, but this was simply how revolvers used to work. The Webley-Fosbery revolver had a manually applied safety, but this is likely just a work around for there being no practical way of fitting a conventional revolver safety mechanism into the pistol due to the recoil operated slide mechanism.