>>495.497
英語圏でも話題になってるが、女王の遺体はエンバームされた。

With Queen Elizabeth's coffin being kept open for the public,
people have wondered how they managed to preserve her body.
It has now been confirmed that the Queen was embalmed.
Additionally, a report from CBS said:

“Following a centuries-old tradition for royals, the Queen’s coffin is lined with lead,
which helps prevent a body from decomposing for longer.
The lead also makes the coffin significantly heavier, meaning eight pallbearers will be needed to carry it.”

方法については「エンバーミング」「Embalming」でウィキってみ
自分の遺体を展示せよと遺言したベンサムの自己標本(auto-icon)と頭部も見もの