Hundreds of years ago, Britain didn't have just one king - it had lots! Celtic kings and princes ruled Scotland, Ireland and Wales, and everything else was divided up between tribes of Anglo-Saxons.
Each tribe had its own king. Sometimes one king became more powerful than the others, and for a while he would be overlord or chief king. Then in early 800s, bands of Danish Vikings from northern Europe began attacking Britain. In 878, the Saxon King of Wessex, Alfred the Great won a great battle against the Danes and forced them to agree to peace. Much of Britain was divided into Danish land (the Danelaw) and Anglo-Saxon Land (England).
Gradually the Danes and the Saxons learned to live together and in 924 Athelstan (Alfred's grandson) became king of both Saxon and Danish lands - the first 'King of England'. But England wasn't peaceful for long. After about 60 years, the Viking raids began again - and only ended in 1016, when the Danish King, Canute, became King of England.
ANGLO-SAXON KINGS
924-939 Athelstan; (15yrs, 102 days)
939-946 Edmund; (6yrs, 210 days)
946-955 Edred; (9yrs, 181 days)
955-959 Edwy; (3yrs, 313 days)
959-975 Edgar; (15yrs, 280 days)
975-978 Edward the Martyr; (2yrs, 253 days)
978-1016 Ethelred the Unready; (38yrs, 36 days)
1016 Edmund Ironside; (222 days)
DANISH KINGS
1013 Sweyn Forkbeard; (a few weeks)
1016-1035 Canute; (18yrs, 347 days)
1035-1040 Harold I; (4 yrs, 125 days)
1040-1042 Hardecanute; (2yrs, 83 days)
ANGLO-SAXON KINGS (continued)
1042-1066 St Edward the Confessor; (23yrs, 294 days)
1066 Harold II; (283 days)
NORMAN & PLANTAGENET KINGS 1066-1377
William the Conqueror 1066-1377
William Rufus 1087-1100 (son of William)
Henry I 1100-1135 (William Rufus' brother)
Stephen 1135-1154 (nephew of Henry I)
Henry II 1154-1189 (grandson of Henry I)
Richard I 1189-1199 (third son of Henry II)
John 1199-1216 (fifth son of Henry II)
Henry III 1216-1272 (son of John)
Edward I 1272-1307 (son of Henry III)
Edward II 1307-1327 (son of Edward I)
Edward III 1327-1377 (son of Edward II)
HOUSES OF LANCASTER & YORK 1377-1485
Richard II 1377-1399 (grandson of Edward III, son the Black Prince)
Henry IV 1399-1413 (grandson of Edward III, son of John of Gaunt)
Henry V 1413-1422 (son of Henry IV)
Henry VI 1422-1461 (son of Henry V)
Edward IV 1461-1483 (great grandson of Edmund of York, Edward III's youngest son)
Richard III 1483-1485 (uncle of Edward V)
HOUSE OF TUDOR 1485-1603
Henry VII 1485-1509 (grandson of Henry V, wife's second husband)
Henry VIII 1509-1547 (Henry VII's second son)
Edward V 1547-1553 (Henry's son by Jane Seymour)
Mary 1553-1558 (Henry's daughter by Queen Catherine)
Elizabeth I 1558-1603 (Henry's daughter by Anne Boleyn)
HOUSE OF STUART 1603-1714
James I 1603-1625 (great-great-grandson of Henry VII)
Charles I 1625-1649 (second son of James)
[Commonwealth 1649-1660] Oliver Cromwell (1649-1658) Richard Cromwell (1658-1659)
Charles II 1660-1685 (oldest son of Charles)
James II 1685-1688 (brother of Charles II)
[Glorious Revolution 1689]
William of Orange (grandson Charles I) and Mary (daughter James II)
[William and Mary 1689-1694; William as William III to 1702]
Anne 1702-1714 (sister of Mary)
HOUSE OF HANOVER 1714-1834
George I 1714-1727 (great-grandson of James I)
George II 1727-1760 (son of George I)
George III 1760-1820 (grandson of George II)
George IV 1820-1830 (son of George III)
William IV 1830-1837 (brother of George IV)
HOUSE OF SAXE-COBURG & WINDSOR
Victoria 1837-1901 (niece of William IV)
Edward VII 1901-1910 (son of Victoria and Albert)
George V 1910-1936 (second son of Edward VII)
Edward VIII 1936 (son of George V)
George VI 1936-1952 (second son of George V)
Elizabeth II 1952 - (daughter of George VI)