The ongoing spat between two authors over the identity of the real King Arthur took a twist yesterday when one of them formally claimed the £50,000 prize being offered by the other if anyone could prove him wrong.

Adrian Grant from Cupar says he has now produced the ‘proof’ that refutes the claim by Glasgow-born David Carroll that King Arthur was a Scot known as Arturius, born Arthur mac Aaedan, who is mentioned in ancient documents.

Grant maintains that Arthur was not a king but a war leader called Arthwys, the son of a fifth century king in what is now east central England, who went north in the late fifth century to be the general of the Britons of Strathclyde in their victories over the Picts and the Scots.

Carroll, however, is so sure that his Arturius as named in ancient documents is the real King Arthur, and that he was Scottish, that he was prepared to pay £50,000 to anyone who can prove him wrong.

Grant told The National he has produced the refutation and has formally claimed the prize.

He says he acknowledges that Carroll “does not stand to gain financially from making the offer of a cash prize for the refutation of his thesis which seeks to identify Arthur mac Aedan as ‘the Arthur of legend’”.

Writing to Carroll, Grant asserts: “The main problem is that while you correctly aimed to attack the idea of a southern Arthur you picked the wrong alternative... you will see that your argument does not stand up and on this basis alone, I should win the prize.”

Grant also states that because of the rules set by Carroll, the prize is “inherently unwinnable.”

Both writers agree that Arthur was a Christian, that he was active in the late sixth century, that he fought against the Picts, but disagree on the number and location of the battles he fought.

They also agree that Arthur had a sister called Morgan, who was married to Urien of the kingdom of Rheghed.

They also agree that the legend is indeed a ‘corpus’ not only of more that one figure but of fictional characters as well. Grant, however, adds that “this does not mean that there was not a real person at the root of it all.”

He does agree with Carroll on one other issue: “I largely agree that people have been looking for Arthur in the wrong place because they have been given bad steers by so-called historians of the past – for a variety of reasons.”

Apart from that, the two authors disagree on almost everything else.

Carroll has already stated that Arturius, the man at the centre of his theory, is as so named in the Life of St Columba written by Adomnan, Abbot of Iona.

He is named as Arturius by Adomnan,” said Carroll, “and there is so much else that fits the stories of Arthur. Arturius was the son of a sixth century Scottish king called Aiden. There is no doubt in my mind that Arturius is the real King Arthur.”

He added: “Both were active in the sixth century, both died in battles against the Picts, both were Christian, both fought alongside Urien and other British kings and both had a sister called Morgan – a name unheard of in sixth and seventh century records.”

David Carroll could not be contacted last night, but has already been in contact with Grant to say he had not done enough to disprove his ‘Arturius’ theory.

We will carry Carroll’s response when we receive it.