This is a grave from the Victorian age when a fear of zombies and vampires was prevalent. The cage was intended to trap the undead just in case the corpse reanimated.
ARE YOU GUYS SERIOUS?!
This was to protect against body snatching!
Here: educate yourself.
Seriously? Trust me, fear of premature burial was there (it’s been stipulated in more than one will that the head is to be cut off before burial “just in case”, so that the person doesn’t wake up underground), but if there were any legitimate fear of zombies, no one would have ever even thought of a “Waking Mortuary”, where rich British people stayed after death, until they started to decompose. No one actually woke up in any of those Waking Mortuaries, by the way.
Even that fear was far more transient a cultural standpoint than the totally legitimate fear of body-snatchers, especially in England. France allowed dissection of executed criminals and unclaimed cadavers from the Revolution onward, but England didn’t allow any sort of dissection (aside from on executed felons - and they had nowhere near as many as in France) until nearly 50 years later.
The only way anatomists could get bodies for quite a while was by buying them from “ressurectionists” who would rob fresh graves. Or, if given the opportunity, would just kill transients and sell those bodies. It was the case of Burke and Hare, who started as resurrectionists but later started killing family-less boarders at Burke’s boarding house, that finally brought the need for cadavers by the medical community to the forefront of the judicial system.
There was finally a law passed in 1832, after the Burke/Hare case, allowing unclaimed corpses to be used in dissection research. This drastically cut down on the number of graves that had bodies stolen from them, but until cement vaults and other structural/security components became standard on graves (not until the 1930s in some places), rich people DID still have their graves robbed for any valuables they may have had on them.
So yeah. Resurrectionists. Body snatchers. Literal grave robbers. All problems. Zombies? Not so much.