Diana and Charles were, in effect, victims of the last surviving gasps of what might be termed "Victorian values" when it came to what was considered appropriate marriage material for an heir to the British throne.

A good deal has changed in Britain since the early 1980s, but way back then it remained simply inconceivable that the heir could marry so spectacularly "beneath himself" as to propose to a mere commoner. Diana herself – who was the daughter of Earl Spencer, a nobleman in the second rank of the British aristocracy – was, in fact, considered only just appropriately qualified by birth to marry Charles; prior to this, the sole reigning monarch since the Norman Conquest who had, in effect, stooped to marrying one of his own subjects had been Edward IV (1471-83), whose marriage to Elizabeth Woodville – a beautiful widow who came from the ranks of the minor aristocracy – was considered so inappropriate at the time that the couple had to wed in secret. Much more recently than that, of course, there had been the terrible example of Charles's uncle Edward VIII, whose determination to marry an American divorcee, Wallis Simpson, had caused such serious consternation that he was forced to abdicate the throne in order to wed her (1936). Charles's grandfather, George VI, had married an aristocrat, Elizabeth Bowes-Lyon (1923), but he had not been first in line to the throne at the time, and succeeded only because of the abdication of Edward VIII.

Charles's problem, back in 1981, was a very severe shortage of potential brides who met the minimum criteria to marry him – in this sense it seems pretty clear that Diana was seen neither as the first possible choice, nor really necessarily as an especially suitable one; it was simply that she met the standards when almost nobody else did. Put bluntly, the requirements that the royal family and its courtiers had in place for Charles was that his bride should be, [i] ideally a Protestant princess from a reigning European royal family, and [ii] most definitely, a virgin. Because no princess of suitable age and faith was considered right for the prince, there was quite a bit of discussion at the time that he might end up marrying a Catholic princess instead – the prospects of Marie Astrid of Luxembourg were quite frequently talked up for a time. But the prospect of a Catholic queen was, in itself, pretty controversial at a time when an Act of Parliament still prohibited the English monarch from being Catholic, and so ultimately Charles was encouraged to consider Diana instead. The most obvious reason why he wasn't encouraged to marry a suitable woman of his own age was that the royal family were way behind the times when it came to sexual mores. There simply weren't any 25+ year old virgins of aristocratic birth around, and Diana was pretty unusual, in 1981, in being still a virgin at the age of 20.