In Shakespeare’s Henry IV Part I Hotspur refers irritably to Owen Glendower’s tales “of the dreamer Merlin and his prophecies … and such a deal of skimble-skamble stuff”. He leaves us in no doubt that Welsh divination is all “rambling” and “worthless” nonsense (as Brewer’s Dictionary of Phrase and Fable interprets it). Prophecies attributed to Merlin have had mixed reviews over the centuries, largely depending on the mindset of the audience. Have they any relevance now?
Trying to divine the future has been a human activity that long predates press horoscopes. The Old Testament had its prophets and its interpreters of dreams such as Joseph, and Insular Celts were no less keen on divination than other cultures. However, unlike the personal divination familiar to folk practices, most foretelling that has been recorded historically relates to the political fates of societies, peoples and their rulers. To this latter class belongs the tradition of Merlin’s prophecies.
Tintagel has been associated with King Arthur for a millennium, particularly after Geoffrey of Monmouth wrote and published his History of the Kings of Britain in the early 12th century. Though now often claimed as the site of Arthur’s court or castle, Geoffrey cited Tintagel merely as the site of Arthur’s conception.
Uthr, Uthyr, Uther
Uther Pendragon, whose last name derives from a Welsh title pen dragon or pen draig (‘head dragon’ or ‘chief warrior’), is a rather strange and shadowy figure. His chief claims to fame are his sobriquet Pendragon and his being the father of King Arthur. In the 11th-century Welsh poem numbered 31 in the Black Book of Carmarthen — Pa Gur (‘Which man?’) — he appears as uthir pen dragon, a warrior whose servant is in Arthur’s retinue: uthr in modern Welsh means wonderful or terrible, perhaps even awesome in the sense of ‘producing awe’. 
According to Geoffrey of Monmouth (c 1095-1155) the name Pendragon came from a comet which supposedly gave Uther victory over the Saxons.  Geoffrey may have had in mind a comet of 508 with several tails, or may even himself have remembered a spectacularly brilliant comet of 1106, noted in a Welsh chronicle as “a star wonderful to behold, throwing out behind it a beam of light of the thickness of a pillar in size and of exceeding brightness, foreboding what would come to pass in the future”. 
The word dragon in Welsh seems to have been a customary title for a warrior, however, as Maelgwn of Gwynedd (d 547) was called by his contemporary Gildas ‘the dragon of the island’, insularis draco (possibly Gildas meant the isle of Anglesey).  A plausible suggestion has been that Uther is therefore a ‘ghost’ and that the person in Arthur’s retinue mentioned in Pa Gur is merely the servant of uthir pen dragon, the ‘fierce chief warrior’.