As an interesting aside on Richard III, I just saw an interesting program courtesy of You Tube. It was a 2004 show by Tony Robinson entitiled Britain's Real Monarch (for those of you unfamiliar with him he's an interesting chap who does an English version of History's Detective) on the possibilty that Edward IV was, in fact, illegitimate, thereby invalidating the claim of the Tudors (and their descendants) to the crown. The proof seems to hinge on the fact that Edward's Father was off in France fighting about the time he was supposed to have been conceived. If correct, this would mean that the throne would, in fact, revert to the Plantagenents. But, you might think, that Richard III was the last of that line and it ended on Bosworth Field. Apparently not. It appears there is a line of descendents through the Hastings family and the Earl of Loudon and, mirabile dictu, a descendent lives on in Australia, Michael Hastings. Actually a regular bloke who believes that Australia should be a Republic and sever its ties to England.
Here are the arguments from Wikipedia:
" In a 2004 television documentary it was revealed that records discovered in the archives of Rouen Cathedral indicate that from 14 July to 21 August 1441 (the five-week period in which Edward is likely to have been conceived) Edward's supposed father was away on campaign at Pontoise, several days' march from Rouen (where Cecily of York was based), and that prayers were being offered at the cathedral for his safety. No evidence has survived which indicates that Edward was born prematurely. The programme also drew attention to the fact that the christening celebration of Edmund, Earl of Rutland, the second son of Richard and Cecily, was a lavish affair at the cathedral, whereas the christening of Edward, the firstborn, was low key, and in a side chapel. The programme concludes that Edward was illegitimate. For more details see the TV programme Britain's Real Monarch.
Counter-arguments to this theory are that the Duke of York could have returned to Rouen from Pontoise, because there was a road in English hands. The absence of evidence does not mean that Edward was not born prematurely. Because of high infant mortality, baptisms were often performed quickly, and Cecily had already had children who had died young. Richard, Duke of York, did not contest his paternity, and Edward IV could in any case claim the crown from Henry VI by right of conquest, whether he was a legitimate child or not. Even if he were illegitimate, Edward still had a direct (albeit legally barred) blood-claim to the throne through his mother Cecily, who was a great-granddaughter of Edward III through John of Gaunt and his illegitimate daughter (Cecily's mother) Joan Beaufort, Countess of Westmorland. Although this claim is via an illegitimate line, it is no weaker than that of Henry Tudor, who dislodged the House of York from the throne in 1485."