"I've just been watching "The Queen" on STV where a stag was sadly shot."

Why sadly?

Cannot think of any worse fate for a Stag, particularly a Red Deer Stag, than dying of "old age", which equates to dying from starvation. After they have passed their "prime" deer go through a process of what is called "running back", their teeth wear down to a point where they cannot feed and they lose strength, vitality and condition, they can no longer maintain their position or even a place in the herd and they suffer a long, lingering solitary death.