I have done my best to examine the inscription on the so-called gravestone. Point 1: about half the runes are unrecognisable. Point 2: Those runes that are recognisable do not go to make words in any language known to me, and certainly not in anglo-saxon, norman french or Latin which an englishman in the twelfth century might be expected to have used. Point 3: I can see no evidence of the name Hurech in the inscription. (And, incidentally this would not have been a mans surname - surnames were NOT in general use in England in the twelfth century)
The rest of the evidence adduced seems to be on a par with this fundamental flaw.
As to the entertainment value of this piece - about one third of the episode is padding - cars driving through the desert, etc..