Curators made the remarkable discovery inside a war-time service envelope with a hand-written note identifying the contents as being from an ancient Egyptian tomb originally built around 1290 BC.
The ancient textile - described as a “curator’s dream” by the museum’s ancient Egypt expert - was painstakingly unwrapped and dried out by conservators over nearly 24 hours before.
It revealed a hieroglyphic inscription identifying the owner as the previously-unknown son of the Roman-era high official Montsuef and his wife Tanuat, and depicts the deceased as the god Osis.
Experts at the museum say the inscription and the recorded deaths of his parents in 9BC has allowed them to date the shroud almost precised back to 9BC.
It will be going on display at the end of the month along with other exhibits drawn from the tomb. It was originally built for a police chief and his wife, looted and reused several times over more than 1000 years, and sealed off in the early 1st century before being discovered
Dr Margaret Maitland, senior curator at the museum, said: “To discover an object of this importance in our collections, and in such good condition, is a curator’s dream.
“Before we were able to unfold the textile, tantalising glimpses of colourful painted details suggested that it might be a mummy shroud, but none of us could have imagined the remarkable figure that would greet us when we were finally able to unroll it.
“The shroud is a very rare object in superb condition and is executed in a highly unusual artistic style, suggestive of Roman period Egyptian art, yet still very distinctive.
“It is extraordinarily rare that we have such an incredible group of objects belonging to a whole ancient Egyptian family in our collections.
“To have been able to expand this group of objects with this new discovery is very exciting, and further enhances our understanding of the story of this wonderful tomb and its occupants.”