King George VI was originally buried in the royal vault following his death in 1952, and was then moved to the chapel following its construction in 1969. Queen Elizabeth’s mother was buried there in 2002, and her sister Margaret’s ashes were also stored there that same year.

As was the case with many areas of her life, Princess Margaret opted to defy tradition and be cremated instead of going through a traditional burial.

Source: https://www.distractify.com/p/was-queen-elizabeth-cremated