Speculation: Was Catherine's marriage to Henry VIII legal?

Background Information: In 1501, sixteen-year-old Catherine of Aragon sailed to England from Spain to wed Prince Arthur, Henry VIII's older brother. Arthur had always been frail and died within months of their marriage, leaving Catherine as the widow Princess-Dowager of England. When Henry VIII came to power in 1509, he received a dispensation from Pope Julius II to wed Catherine, his brother's widow and in the eyes of some, his sister. She took with child many times but their only child who lived past infancy was a daughter, Mary Tudor. Henry VIII needed an heir to keep alive the Tudor dynasty and maintain unity in his kingdom; but before long Catherine became barren. Henry knew by 1526 that he had to find some way to get a legitimate son.

Casting aside all other factors such as Henry's dire need and belief that England and the Tudor dynasty would survive only under a male heir, his passionate longing for Anne Boleyn, and the fact that without a king to succeed him European powers or England's nobility would swoop in and tear the land apart, should Henry have divorced wife number 1? The question is not so much should as it is could he legally annul his marriage to Catherine?

Henry's statement was that when Catherine wed his brother, Arthur, in 1501, their marriage was consummated and so thus, having had intercourse with her brother, having such with Henry would be incest. He took this quote from Leviticus: "If a brother is to marry the wife of a brother they will remain childless" and cited it as the reason why he and Catherine had no sons. Catherine adamantly claimed that she went to Henry's bed a virgin, never once having sexual intercourse with her brother; even so, the couple had a dispensation from Pope Julius II. Only Pope Julius could look into or recall the dispensation, but he had died and Clement, in a sticky situation with the Empire, could -- but he was in no position to.

Alas, was the marriage truly illegal? Personally, I would say yes, and not simply because I am a die-hard Anne Boleyn lover. In those times, marriage and sex were as one: it was as good as impossible for a couple to wed and never bed. I don't doubt that Catherine and Arthur at some point had intercourse, and whether or not they did, the marriage still had witnesses and was legal. I do believe that in those days, no dispensation should have been able to outweigh the word of God, as Henry stated.

Either way, Rome never came to a conclusion and Henry had to take matters into his own hands, infamously severing all ties to the R.C.C. (Roman Catholic Church) and creating his own, the Anglican Church (which was still Catholic). In the eyes of the Empire and Rome, Henry became free to marry only after the death of Catherine of Aragon, viewed by some as Henry's one and only true wife.

My Opnion: Back in the ways of the sixteenth century, I believe all marriages of Henry VIII were legal save for this, but today I would say that all six marriages happened and can still be counted. Henry annulled all marriages save for those to Jane Seymour and Catherine Parr, using means of pre-contracts and affinity to squeeze out of the other four.