The head of the crosier is made of gilded copper and decorated with gilded silver medallions.

Rare treasure found by chance in the grave of a mystery abbot at a ruined mediaeval abbey will go on display after lying undiscovered for more than half a millennium.

The silver-gilt and copper crosier, the staff of office shaped like a shepherd’s crook held by high-ranking members of the Church, was found along with a jewelled ring during emergency repairs carried out in 2010 at Furness Abbey in Cumbria.

Both items will go on display at the abbey over the May bank holiday after excavations at the site unearthed the items in the undisturbed grave of a mystery abbot – thought to be one of the heads of the monastery.

An initial examination of his skeleton, in the care of Oxford Archaeology North, indicated he was probably between 40 and 50 years old when he died.

The grave – which could date to as early as the 1150s – also included the decorated crosier and gemstone ring and was situated in the presbytery, the most prestigious position in the church and generally reserved for the richest benefactors.

The head of the crosier is made of gilded copper and decorated with gilded silver medallions showing the Archangel Michael defeating a dragon, and the crosier’s crook or end is decorated with a serpent’s head.

A small section of the painted wooden staff survives, as do remains of the cloth designed to prevent the abbot touching the crosier with his bare hands.

The ring is gilded silver and set with a white rock crystal or white sapphire.

It is possible that a hollow behind the gemstone contains a relic, part of the body of a saint or a venerated person.

Experts have been unable to pinpoint the exact date of the grave, but believe it to be anywhere between 1150 and the 1500s.

Kevin Booth, senior curator at English Heritage, said: “This is a very rare find which underlines the abbey’s status as one of the great power bases of the Middle Ages.

They were discovered in the undisturbed grave of a mystery abbot thought to be one of the heads of the monastery

“While we don’t yet know the identity of the abbot, he was clearly someone impor­tant and respected by the monas­tic community.

Given that the crozier and ring have been buried for over 500 years, they are in remark­able condition.”

Founded in 1124 by Stephen, later king of England, the monastery was originally located at Tulketh, near Preston, but the monks moved to Furness in 1127.

The abbey, now looked after by English Heritage, first belonged to the Order of Savigny and then to the Cistercians.

In its heyday, Furness knew prosperity on a huge scale, and, at the time of the dissolution of the monasteries in the 1530s, was the second-richest Cistercian monas­tery in England.

The importance and wealth of the abbey is reflected in the quality of the still-standing red sandstone remains, which inspired both Wordsworth and Turner.