For the best part of a century it has sat in storage at Norwich Castle Museum, but now the remarkable secrets of a crumpled linen sheet have been unravelled.

Experts from the British Museum have discovered the secret of the fragile bundle: it is a rare, ancient Egyptian burial shroud, at least 3,000 years old and covered with black and red hieroglyphic writing – spells from the Egyptian Book of the Dead.

Studies have even established the name of the woman around whose mummified remains it would once have been wrapped.

The bundle was given to Norwich Castle Museum in the 1920s by the daughters of Jeremiah James Colman, of the mustard-making dynasty, who had obtained it during a visit to Egypt in 1897. A leather-bound catalogue, embossed with Egyptian floral motifs and detailing the 'Egyptian curios', was made by the Egyptologist, James Quibell, who was a keeper at the Cairo Museum.

While some of the objects had comprehensive details of where they were bought, all that was listed about the shroud was: 'Linen sheet: covered with inscriptions from the Book of the Dead. The mummy in the coffin was often covered with a linen sheet of this kind.' It caught the attention of Faye Kalloniatis, research associate responsible for the Egyptian collection at the Castle Museum.

Through a tie-up between regional and national museums, it was packed up carefully in January and taken to London so experts could study it.

British Museum conservators built a tent out of plastic tubes and sheeting in which to place the shroud so the work could be done. Ultrasonic humidifiers were used to control the environment so the shroud could be unrolled without damaging it, and after three days of careful work the 1.4m by 1.6m shroud had been revealed.

Ms Kalloniatis said: 'As they opened it up we saw it was completely filled with rows of red and black inscriptions, which are spells from the Book of the Dead. They are spells which dead people needed to get to the afterlife, and what's really interesting is that it is rare to find them inscribed on a shroud like this. It's much earlier than most, dating back to the 18th dynasty, which would be about 1550BC. Later on they used vignettes on parchment for the spells from the Book of the Dead rather than inscrip-tions on shrouds, so it is quite rare.'

The hieroglyphs are still being translated, but experts have confirmed it was wrapped around the mummified remains of a woman of status called Ipu, daughter of Mutresti. Ms Kalloniatis said: 'Another interesting thing is that it turns out it is a fragment of a piece which is held in a museum in Cairo, so it would once have been a much bigger shroud.

'It has just been the most amazing project.'

Because the shroud is so fragile, it will probably not go on permanent display once it comes back to Norfolk, although a short-term exhibition on it is in the pipeline.

But there will be a chance for people to view it and find out more about its secrets on Tuesday, May 24, between 10am and 5pm, at a study day called 'Unveiling the Norwich Shroud' held in Norwich Castle Museum.

It will include a series of illustrated talks on how the shroud came to be at the castle, the work of the British Museum in conserving it, the results of scientific analysis and what has been discovered by translating the text on the shroud. The event is free once admission to the castle museum is paid for, but booking is essential by calling 01603 495897.

You can find out more about the project by visiting http://blog.britishmuseum.org/category/conservation-2/norwich-shroud