“Avalon: The Return Of King Arthur. Book Six of the Pendragon Cycle” by Stephen R. Lawhead
"It has been foretold:
In the hour of Britain’s greatest need, King Arthur will return to rescue his people.
In Portugal, the reprobate King Edward the Ninth has died by his own hand.
In England, the British monarchy teeters on the edge of total destruction.
And in the Scottish Highlands, a mystical emissary named Mr. Embries—better known as “Merlin”—informs a young captain that he is next in line to the throne. For James Arthur Stuart is not the commoner he has always believed himself to be—he is Arthur, the legendary King of Summer, reborn. But the road to England’s salvation is dangerous, with powerful enemies waiting in ambush. For Arthur is not the only one who has returned from the mists of legend. And Merlin’s magic is not the only sorcery that has survived the centuries."
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