radiocarbon dating has revealed the Kirkwall Scroll, a rare wall hanging in the care of a masonic lodge in Orkney, is a medieval treasure worth several million pounds.

Cambridge historian Andrew Sinclair claims the little known scroll is second in value only to the famous thirteenth-century Mappa Mundi which hangs in Hereford Cathedral.

''It's beyond price,'' says Mr Sinclair, who heard about the scroll while researching the history of the St Clair Earls of Orkney. ''Its significance is immense. This will demand the rewriting of Scots medieval history.''

He claims radiocarbon dating points to the 18ft sailcloth as being fifteenth century.

The St Clair Earls of Orkney were associated with the legendary Knights Templar, and the family stronghold in Midlothian is the site of Roslin Chapel, built by Orkney Earl William St Clair in the fifteenth century.

The chapel is well known for its Masonic connections and symbolic carvings.

''The operative side of the craft, connected with the trade guilds and stone masons, was also strongly associated with the St Clairs,'' says Roslin Chapel's exhibition director Bob Brydon, ''so there's little doubt the Kirkwall Scroll has very significant implications.''

Mr Brydon is not convinced the scroll is fifteenth century - ''It's quite feasible it's a copy of an earlier document'' - but because of the symbolism, agrees it is unique and, in Masonic terms, priceless.

Although the Kirkwall Lodge's own archive records the gift of a symbolic floorcloth in the eighteenth century by a William Graeme, lodge members disagree about whether this was the Kirkwall Scroll.

Confusingly, the University of Oxford research laboratory which did the dating, supports both dates. ''We analysed material from the Kirkwall Scroll on two occasions,'' said a spokesman from the archaeology and history of art department. ''The first sample taken from the outside edge of the material was possibly eighteenth or early nineteenth century. The second piece which came from the central panel produced a much older date - fifteenth or early sixteenth century.''

A senior lodge member from Kirkwall says they have a possible answer: ''The cloth has been joined at some stage. You can clearly see where the two side panels interlink with the centre panel.''

London-based Scots businessman Niven Sinclair, who has researched his St Clair ancestry, agrees: ''The symbolically Masonic content which ties in with the Knights Templar is in the central panel. I'm convinced the outer panels are more biblically connected later additions.''

However, a statement by Mr Andrew Sinclair that the scroll should be removed for safekeeping has angered the lodge. A spokesman said: ''Anything is priceless if you've got a market for it, so his sensation-making claims of it being worth millions mean nothing. It is priceless to us and we have safeguarded it well for more than two and a half centuries. No-one can have access without special permission and it is protected from the light, so we would urge 'leave well alone'.''