Monarchy is very much a family business. According to the law of primogeniture, the eldest son should follow his father on to the throne. The statistics are surprising, however. I include some forgotten figures among the forty-eight who have been proclaimed King or Queen of England.
The unhappy Lady Jane Grey reigned for only 9 days – at fifteen, she was pushed on to the throne by her father-in-law. Other largely forgotten reigns are those of Henry the Younger, who ruled jointly with his father Henry II between 1170 and 1183 and that of Louis, heir to the King of France, also proclaimed King of England in 1216. For six months, he ruled the lands south of the Wash.
Henry VI confuses the statistics as he managed two reigns or, according to Shakespeare, two parts. In 1461, the King was deposed and replaced by Edward IV and so concluded his first part. Unusually, Henry was not filleted, beheaded, drowned in Malmsey wine, nor disposed of in any of the ways so popular in medieval times. This concession allowed him to return for a final flourish. (I have counted Henry as only one monarch, though.) A crowned king could not be crowned again and so Henry had to be ‘readopted’, a curiously modern term; he was eventually murdered by his cousin.
Seven Lord Protectors also ruled but only two did so in their own right. When Oliver Cromwell died in 1658, the belief that the son should succeed the father was so ingrained that the council of state named Oliver’s son, Richard, as the next Lord Protector. England was 300 years ahead of North Korea in trying to establish a hereditary republic. Richard Cromwell was a true survivor and outlived Charles II, James II, William III and Mary II. In 1712, Richard died peacefully in his own bed, 53 years after he had given up trying to rule Britain.
The surprise is that only nine of the 48 rulers to succeed were the eldest child of the previous monarch. In 1272, Henry III was succeeded by his first son – Edward I – and, for the next 105 years, eldest son followed their fathers. This is the longest period of elderly succession in the 10 centuries. In 1307, Edward I was succeeded by his eldest son, Edward II. Then, in January 1327, Edward II abdicated, to be succeeded by his eldest son, Edward III. Edward II was murdered at the end of the year to prevent any comeback on his part.
When he died in 1422, Henry V was succeeded by his son, Henry VI. It would be another 125 years until the first son again followed his father on to the throne. In 1547, Edward VI succeeded the flamboyant Henry VIII. The year 1727 saw the next ‘correct’ succession when George II became King after the death of his father, George I. The next father-to-eldest-son succession took place in 1820, when George IV took over from his ‘mad’ father, George III. It would be eighty years before another first-born inherited: Edward VII, in 1901. In 1936, Edward VIII, the first son of George V, was crowned but abdicated. Then, in 1952, George VI’s eldest daughter, Elizabeth, followed her father.
The eldest child did not succeed for many reasons; the catalogue of mishaps and tragedies included shipwreck, murder, epidemics, appalling medical care, conspiracies, exile, execution, a wayward cricket ball and many other slings and arrows of outrageous fortune. Of the first-born who got there in the end, six were called Edward. Often there was rivalry between and within the generations. Since 1066, sons have plotted against their fathers, especially when the monarch lived a ludicrously long time in opinion of his child. To date, no British monarch has reigned into their nineties. George III died at 81; Queen Victoria lived to 81. The present Queen, Elizabeth II, is the oldest person ever to occupy the throne.

Edward VIII in royal robes, A copy was only discovered after the publishers moved offices and it is believed the original portrait by Albert Collings was lost in the war
Some royals have not been able to cope with the pressures. George III was not the first to have some sort of breakdown. The long history reveals a number of monarchs were psychologically fragile. Around 1370, Edward III suffered some such episode, as did Henry VI on a number of occasions – most dramatically around 1453 – and Henry VII in 1503.
from a book “Bring Them Up Royal” by David Cohen