A stone discovered by chance on the Isle of Canna is Scotland's first known example of a bullaun "cursing stone", experts have revealed.

Dating from about 800 AD, the stones are associated with early Christian crosses - of which there is one on the isle.

It was found in an old graveyard by a National Trust for Scotland (NTS) farm manager.

The stone is about 25cm in diameter and engraved with an early Christian cross....