Princess Diana's Coffin Weighed A Lot More Than You Realize
If you've ever served as a pallbearer, you've realized what an extremely difficult job it is. To say nothing of the emotional gravitas of the job, there's also the fact that you'll be carrying an extremely heavy load, literally as opposed to figuratively. Between the weight of the body and the weight of the coffin, each pallbearer is shouldering their share of a quarry that can weigh several hundred pounds.
For members of the British royal family, however, the guards who carry their coffins are tasked with carrying even more weight (fortunately, they're military men who are fit and adept at physically-demanding duties). That's because British law and custom dictate that royals are buried in lead-lined coffins. Further still, the law says that bodies interred above the ground (in tombs, as opposed to, say, buried in the ground) must be in lead-lined coffins. According to the Metro, Princess Diana's coffin weighed just over 550 pounds (not counting the weight of the body within).
The reasons for this are practical and, indeed, a bit on the gruesome side.
Lead-Lined Coffins Preserve The Body
Before continuing with this discussion, it bears noting that burial and entombment are two different things. Burial is just that: burying someone beneath the ground ("six feet under," as the old saying goes), while entombment generally means being placed in a tomb above the ground (such as the graves of thousands of people in cemeteries across New Orleans).
As the Metro explains, British law requires that if the deceased is to be entombed rather than buried — or their body is going to lie in state for a period of time — their coffin is to be lined with lead. Princess Diana, for example, was entombed above the ground, according to Parade, and legally, her coffin was required to be lined with lead.
Now for the gruesome: Lining a coffin with lead will contain the smell of the decomposing body, which will be important for the dignity of the queen as well as for the comfort of the tens of thousands who are expected to file past her coffin as she lies in state. Further still, the airtight seal slows the decomposition of the body for up to a year, protects the body from toxins, and prevents the embalming process from leaching into the environment.