There are several references to swords in stones and dragons etc in the mythology of the Sarmatians, I know, but how far back do they go? Is there evidence of these parts of their mythology in the period before the Sarmatian defeat by the Romans on the Danube (I forget the date - 170ish?)and that the traditions were old enough to lend themselves to the story?

There is evidence in Britain of the deposition of swords and cauldrons in ritual contexts going back at least to the Bronze Age - a millenium before the Sarmatian cavalry were brought to Britain.

This Sarmatian theory does have facts to support some of the suppositions it makes, but they cannot be proved to be linked. Linda Macor, one of the main proponents of the hypothesis, gives some very convincing accounts - until you read between the lines and start asking questions - and then it does not seem to stand up to too much examination.

impossible to tell how far back i reckon. my theory on swords is that the first people to smelt bronze or iron then make swords from stone? must have felt something magical had gone on. the power this would have given them would have been huge against stone and wood wielding neighbours. dragons must be dinosaur fossils probebly pteradactyl type. these are still found in the gobi desert and siberia where the sarmatians traded and possibly explain the chinese dragon links.with the arthur connection i feel that over time stories have intermingled with myths from all over europe and beyond and many countries have similer tales.

There is actually quite a bit of evidence that Arthur of legend was based on a ‘Dark Age’ Arthur and not one of the 2nd Century. Even if we exclude Nennius’ two entries about Arthur for 518 and 539 and Y Gododdin there’s suddenly in influx of Arthur type names after this period.

There have been several interpretations as to the line about Arthur in the Gododdin. One, already mentioned, is that he was a legendary figure to be compared with, but the other is that they are comparing Gwawrddur to someone in living memory, and someone who was either a man of the Gododdin or Gwenydd, who fought along side them. It also sounds almost like an insult on the face of it but if interpreted that, although Gwawrddur was not like Arthur in looks or stature he was still bloody good!

It should also be mentioned that Lucius Artorius Castus was not a Sarmatian, he was an Italian who commanded a Sarmatian unit in Britannia.

The dragon motif is highly likely to come through of one of the following reasons:
Arthur was a Magister Draconii - head of a cavalry unit.

Warriors of the period were called ‘dragons’ and Arthur was a Head Dragon, or Pen Dragon in Brythonic.

He was a war band leader of Gwenydd (Venodotia/Guenedota). This kingdom was associated with the dragon.

Having said all that, it’s only Geoffrey of Monmouth who started this by saying Uthyr Pendragon was his father, so Arthur automatically became Arthur Pendragon as if Dark Age people suddenly developed surnames. Arthur would only get this epithet by being a 'pen dragon'. Some think that his name is an epithet anyway - either meaning 'arth' (bear) 'uthr' (terrible/horrible) or from 'Aturus', from Acturus the star: Guardian of the Bear - and that his proper name was something else.

There’s much debate about the sword and its throwing into the lake, but this is a later addition to the legend even if it is based on Celtic votive offerings. In British (Welsh) tradition his sword is indeed a great sword but not magical. It’s given a name along with all his other weapons: 'caledfwlch' (Old Welsh something like ‘kaletvuilch’ like the Breton ‘kaledvoulc'h’), often said to mean ‘hard breaker’ or ‘hard lightening’ although I’ve know idea why as it’s more likely ‘hard' (caled) 'difiler(r)’ (fwlch - modern Welsh bwlch). Some think it was inspired by Fergus mac Roich’s sword, 'Caladbolg', which means ‘hard' (caled) 'belly' (bolg) - Welsh for belly is ‘bol’. It could have been inspired by it or they were both a type of sword.