Conservation experts are currently carrying out work to ensure the 3,000-year-old Egyptian priest and his inner and outer coffins look their best before going on display at the new £20m Leeds City Museum which opens on September 13.

Leeds once boasted a fine collection of mummies but they were destroyed in a World War Two air raid in 1941 and only Nesyamun survived.

He will be one of the attractions in the new museum's Ancient Worlds gallery.

Emma Bowron, conservator at Leeds City Museum's Discovery Centre, Clarence Dock, where the work is taking place, said Nesyamun's remains would be moved on to a foam base to give it more stability ahead of its move to the museum in Millennium Square.

She added: "Most of the work is being done on the inner coffin lid. It includes repairs and some strengthening and cosmetic work."

The mummy was purchased for the museum of the Leeds Philosophical and Literary Society in 1823 by John Blayds, a wealthy Leeds banker.

A year later the Leeds Intelligencer newspaper described it as "a valuable curiosity if a very rare kind" and claimed "there is not a finer in the British Museum".

Over the years the mummy has been the subject of much scientific study and his coffin also tells much about his life.

He lived during the reign of Ramesses XI, who ruled Egypt 1113-1085 BC. Nesyamun was a priest at the temple of Amun in the Karnak complex at Thebes, which employed up to 80,000 people at its height.

He was a "waab priest," which meant he had reached a certain level purification and was allowed to approach the statue of Amun within the most sacred inner sanctum of the temple.

Nesyamun, who was 5ft 6in tall, was aged in his mid-40s when he died. He had well manicured hands with henna painted on his fingernails suggesting he had a privileged life.

But despite all the investigations, the cause of Nesyamun's death remains a mystery.

Unusually, he was mummified with an open mouth and protruding tongue, leading experts to speculate he may have had a seizure or heart attack or suffered an allergic reaction of some kind and died by choking.