Help me understand the decomposition of the Queens body as it lies in a casket for 5+ days

Hi guys. Not sure if this is the right place to post. Hoping you all can help me understand something about human decomposition. The queen is allegedly inside a coffin at Westminster Palace currently. Being held in a large room- at room temperature, open for public viewing. She is to stay here for several days until her funeral on Monday. How is it possible that the human body can remain in a coffin for 5+ and not begin to severely decompose? Would her body be fixed with Fermaldehyde or is it possible that she’s just not in the coffin and in a morgue somewhere? Thanks!