IT IS known by superstitious actors as "the Scottish play", but a pair of historians are now questioning how much William Shakespeare's Macbeth actually belonged to England's most famous playwright.

In a radio programme to be aired today, Scots historian Fiona Watson and literary expert Molly Rourke claim the story of Macbeth was penned by a Scottish monk on St Serf's Island in the middle of Loch Leven 400 years before William Shakespeare even drew breath.

In Macbeth the Highland King to be broadcast on BBC Radio Scotland, Watson says Macbeth and his wife, Gruoch, were in fact "respected, God-fearing folk".

According to Watson, the "almost entirely fantastical view" of Macbeth and Lady Macbeth drawn by William Shakespeare is lifted, almost word for word in places, from a collection of folklore recorded by St Serf's monk, Andrew de Wyntoun.

The real king Macbeth once made an endowment of land to the monks of St Serf, together with privileged access to the port of Inverkeithing. But in an act of double-cross befitting the murderous play, Wyntoun's work, which he called his Oryginalle Cronykil, portrays Macbeth as a "changeling", or Devil's child.