Dr Andrew Breeze says the correct site of the Battle of Maserfield, or Maserfelth, where Oswald, king of Northumbria, died in 642AD, was actually 20 miles away, at Forden, Powys.
"In a gap between the hills south of Welshpool and east of Forden a Northumbrian army was wiped out," he writes in presenting his findings in the magazine Battlefield, published by the Battlefields Trust.
Oswald came to a grisly end. After being killed in combat his body was hacked to pieces and his enemies nailed up his head and arms for all to jeer at.
But then his body parts were rescued, given proper burial, and miracles started to happen.
Andrew says the main information on the conflict comes from the writings of Bede, who knew little about it or where it was, being more interested in making Oswald out to be a saint and a martyr, and narrating strange events which followed the battle.
One miracle was a horse thrashing about in agonising pain, but when the steed came to where Oswald was killed, the frenzy stopped immediately.
"In this bizarre anecdote is a historical clue. The battle evidently took place on a highway, which was surely an old Roman one. That counts against Oswestry, far from any Roman road."
As for Oswestry's claim, Andrew says: "Anyone who looks up entries on the town or what happened in 642 will be informed that the name means 'Oswald's tree,' which is correct, and that it is called after both St Oswald – which is most unlikely – and a cross, the tree, raised by him, which is quite untrue.
"Fortunately some have rejected the oft-repeated link between Oswestry and the battle."
He cites place-name scholar Margaret Gelling, who drew parallels between Oswestry and Coventry, Daventry, and Braintree, as containing an Old English personal name, plus "tree."
"But she stressed that there was not the slightest reason to take those trees as crosses. Her conclusion was incisive. That nothing connects King Oswald with Oswestry will be 'a shocking heresy to the people of that town, and they will doubtless continue to believe that Oswestry is the place where St Oswald, the Christian King of Northumbria, was killed by Penda, the heathen King of Mercia.'
"How right she was."
With Bede pointing to Maserfelth being on a strategic highway, and Oswestry being far from any old roads, the facts did not point to a battle site there, but did fit a site near Forden, where the Roman highway from Wroxeter entered Wales.
"Decisive proof was given in 1934 by two German scholars. In his dictionary of Old English, Ferdinand Holthausen cited Max Forster of Munich for Maserfelth as 'field or open land of 'Maser,' together with his suggestion that 'Maser' is a Welsh toponym.
"Now, Meisyr is the old name for the remote wooded area west of Welshpool. Work on these forms by German and Welsh philologists provides an answer on the location of Maserfelth.
"Bryn-cae Meisyr and other toponymns in the locality show that Meisyr was known to the English as Maser. Maserfelth will hence be in east Meisyr – closer to England – on the Roman road mentioned by Bede, and within walking distance of Meifod."
Andrew says the exact site is revealed by another Welsh place name, as native bards and chroniclers knew the encounter as Cogwy.
"The Welsh 'cog' can be understood as 'knob, boss, cone,' and it leads to what the Victorian topographer Samuel Lewis described as a vast conoidal rock, surmounted by a ruined fortress, two hundred yards from the mansion of Nantcribba, in Forden parish.
"Modern battle-fanciers will find the summit east of Offa's Dyke and a mile from Forden parish church.
"It was below this rock on a summer's day in 642 that Oswald died. It was there that he was beheaded and otherwise dismembered, his body, it seems, being buried on the spot, with its head and arms left fastened up for Mercian execration of mockery.
"With that, the flimsy claims of Oswestry to be Maserfelth can be dismissed for ever."
Today Nantcribba is privately owned and is a heavily wooded mound, with the rocky outcrop largely having been quarried away.
Andrew lives in Spain, where he is professor of philology at the University of Navarra, but adds: "I am glad to say that the Breezes are a Shropshire and West Midlands family. We can trace our ancestors back to a blacksmith in a village near Pontesbury in about 1850. Our son Patrick Breeze actually lives in Shrewsbury. He is a priest at Shrewsbury Cathedral.
"My interest in the battle really comes from work on Celtic and Old English. I was trained in these and similar languages, like J. R. R. Tolkien. So the whereabouts of 'Maserfelth' is a puzzle known to me since student days in the 1970s."