Will longest-serving heir Prince Charles ever be king?
Queen Elizabeth set to overtake Queen Victoria's record on the throne, with no sign of abdication
As the Queen becomes the country's longest-reigning monarch next month, debate is likely to reignite about whether it is time for her to abdicate and let Charles become king.
The Prince of Wales, who has been waiting first in line since February 1952, became the longest-serving heir to the throne in April 2011.
When he turned 65 two years ago, there was an open acknowledgement that he would increasingly take on more of his mother's duties, with some constitutional experts foreseeing an "unofficial co-regency".
In terms of precedent, there is nothing stopping Charles ascending the throne. But he would be the oldest person to do so. The record was previously held by William IV who was 64 years, ten months and five days old when he became king in June 1830 following the death of his father George III.
Surveys have consistently suggested the British public are not keen on the idea of Charles as king and even less keen on the idea of Camilla, the Duchess of Cornwall, as Queen. A poll in April found that only 53 per cent of people liked Prince Charles, compared to 77 per cent who liked Queen Elizabeth.
The problem, the Daily Mail's Allison Pearson has said, is that the Queen has done her job too well. Who on earth can follow such an act, she asks. "Not Prince Charles, I suspect. We know far too much about his foibles and past errors to revere him as we revere his mother."
Moreover, royal insiders say the Queen regards her position as a job for life and is not for budging. "She's not staying on because of any concern about [Charles's] abilities as a king. The Queen simply feels she must do her duty, and she's never even contemplated abdication," says Sarah Bradford, author of Queen Elizabeth II: Her Life in Our Times.
Harry Mount, author of How England Made the English, says the Queen "could, theoretically, abdicate tomorrow if she wanted". But he says she won't because we don't want her to. "Her constancy and steadfast adherence to a job she believes is for life instils in us a nation-defining sense of confidence," he says. "The longer our Queen stays on the throne, the more secure we all are."