Who Will Be Queen? Before Elizabeth Dies She Could Radically Alter Line Of Royal Succession

Queen Elizabeth II may be the longest-reigning living monarch in the world, but at 90-years-old, she doesn't seem to be showing any signs of slowing down. Despite a weeks-long health scare as the New Year approached, Britain's queen has resumed all normal duties, tending to her daily responsibilities as monarch and overseeing the royal Buckingham palace.

But she may have to make a choice that could transform the line of succession soon. Rumors have abounded in recent weeks surrounding a potential marriage for her grandson, Prince Harry, and his American girlfriend, "Suits" actress Meghan Markle.

Harry's obstacle at hand: Should the Prince of Wales wish to marry his beau, he’d first need to seek approval from his royal grandmother, according to a centuries-old law titled the Royal Marriages act of 1772. The legislation mandated that a prince ask the reigning monarch for permission before asking for a potential-princess’ hand in marriage – Prince Williams’ wife, Duchess of Cambridge Kate Middleton, received express consent from Elizabeth in a hand-signed seal of approval in 2011 – before she could marry William.

"Now know ye that We have consented and do by these Presents signify Our Consent to the contracting of Matrimony between Our Most Dearly Beloved Grandson Prince William Arthur Philip Louis of Wales K.G. and Our Trusty and Well-beloved Catherine Elizabeth Middleton," the queen wrote at the time, stamping the letter with a gold-crusted letter "E."

The approval allowed Middleton's son George to join the official line to the throne, as Markle's children with Harry would ultimately be added to as well.

Approval from Elizabeth, who has enjoyed high approval ratings among the British people for decades, would almost certainly give Markle the reference she needed to officially join the royal family and its line of power. Still, Harry and Markle will probably never hold the throne – Prince Charles, Elizabeth's 68-year-old son, was next in line, followed by Harry’s older brother William and his three-year-old son, Prince George of Cambridge. Prince Harry was currently fifth in line to power.

When that time eventually does come, it could be decades before Britain has another queen. Prince Charles' wife Camilla Parker Bowles, who married the prince after her controversial marital affair in part ended his marriage to Princess Diana, will not become queen. She will instead receive the title of princess consort.

Regardless, changing the royal family's line of succession is traditionally a decision made by a monarch – and one that doesn’t seem to be made lightly by the reigning Queen of England.