The advantages of securing England's vulnerable northern frontier were obvious, but some of Henry Tudor's counsellors, trying to look into the impenetrable future, had felt bound to point out that, if the succession should at any time pass to Margaret or her posterity, then the realm would fall to the King of Scotland, which might prejudice the monarchy of England. Henry, himself a notably astute and far-sighted political operator, had replied that if, God forbid, such a thing were to happen, Scotland would be but an accession to England rather than the other way round, "for the greater would draw the less". This, as Francis Bacon was later to remark, "passed as an oracle" and silenced any doubts.
A little over half a century later Henry VII's granddaughter Elizabeth succeeded to the English throne, Margaret Tudor's granddaughter Mary was Queen of Scotland and already the battle lines were being drawn. Mary's claim to be accepted as her cousin's heir presumptive was undeniable and, in private at least, was not denied by Elizabeth. "For my part I know none better, nor that myself would prefer to her," she told Mary's envoy Maitland of Lethington. But at the heart of their deadly rivalry was Mary's claim to be regarded "not as a second person after the Queen's Majesty, but afore her" and this, too, undeniably existed.
In the eyes of the Catholic world, which had never recognised Henry VIII's famous divorce, Mary had a far better legal right to be Queen of England than Henry's daughter, born during the lifetime of his first wife. Elizabeth had, after all, been bastardised and disinherited by her own father in a still unrepealed Act of Parliament and during her first brief marriage in France Mary had openly quartered the English royal arms with her own.
By the time of her return to Scotland to try the experiment of a Catholic sovereign in a fiercely Calvinist nation, the Queen of Scots' beauty and charm were already legendary but, unlike Elizabeth, she had never had to learn the hard lessons of patience, self-control and self-discipline necessary for survival and her long years of captivity in England were filled with an endless procession of futile, dangerous intrigues. "Alas, poor fool," exclaimed the King of France, "she will never cease until they cut off her head." And so in the end they did, although Elizabeth fought against it to the last. What would the world say "when it shall be spread abroad that a maiden queen could be content to spill the blood even of her own kinswoman".
That Mary had always coveted Elizabeth's crown is not really in question. Just how deeply she had been involved in the plots to seize that crown by violence will probably always remain a matter of debate. But by the 1580s, as the international scene darkened, her guilt or innocence was no longer relevant. Protestant England, feeling increasingly threatened from within and without, could no longer contain her. It was as simple as that.
And now they lie in Westminster Abbey, those two sister queens and tender cousins, closer in death than they ever came in life, beneath the handsome monuments erected by Mary's sons, James I and VI, in the chapel of their common ancestor the first Tudor King, all the passions, all the bitterness and tragedy transmuted by time into dust and marble.
Alison Plowden is the author of `Two Queens in One Isle' (Sutton Publishing, pounds 10.99)