Matilda, daughter of King Henry I of England, *was* her father's heiress.
Henry had 22-24 bastards and a legitimate son, William The Aetheling, who was
drowned in the Wreck of the White Ship on 25 November 1125 ---- ten years
before Henry's death.
So, Henry I had no surviving legitimate son to succeed to the throne.
Matilda, his legitimate daughter, had married Henry V, The Holy Roman Emperor
and was styled as The Empress Matilda in English, as she preferred. Her
husband, Henry V died in 1125 of cancer. The couple had no issue.
Matilda returned to England after the death of her husband and Henry I began
to groom her for succession to the throne. She was widowed and childless as
well as pretty well Germanised [read arrogant and pretentious, in English
eyes], having first gone to the Continent when she was eight years old and
having married Henry V when she was 11.
The British nobles and bishops did not particularly cotton to this
Jennie-foreigner as their future queen ---- but Henry I did his best to secure
their oaths of support that they would loyally defend her claims if she
outlived her father and he left no legitimate son.
Matilda married Geoffrey 'le Bel' comte d'Anjou, Touraine et Maine in 1127.
Now she was Brunhilde with a frog husband in the minds of many of the stalwart
British nobles and bishops.
Henry I died in 1135 without fathering a legitimate son. His death led to a
disputed succession just as had the deaths of the two previous Norman kings of
England, William I 'The Conqueror' and William II 'Rufus'.
When Henry I died on 1 Dec 1135, of a surfeit of lampreys as some say, Matilda
was out of pocket on the Continent.
Stephen, a grandson of William The Conqueror, quickly seized the initiative
and crossed to England to seize the crown where he was accepted as King by the
worthies of London, whose trading connections with Stephen's lands in Boulogne
helped to win them to his side.
Stephen pressed on to Winchester, where his brother, Bishop Henry of
Winchester, persuaded an initially reluctant Archbishop of Canterbury to crown
Stephen as King, the custodian of the treasure to hand over the keys, and the
magnates who were present to accept him as monarch.
Some of the nobles and clerics seem to have abandoned Matilda because they
construed their oath to Henry I to have held only if Henry did not give his
daughter Matilda in marriage to anyone outside the Kingdom without consulting
them.
A Great Civil War ensued when Matilda tried to fight back and reclaim the
throne in 1139. This Civil War lasted until 1153 when Stephen finally agreed
to allow Matilda's son Henry to succeed him on the throne as Henry II
'Curtmantle'. Yes, the one who was married to Eleanor of Aquitaine,
Richardson. Henry II also inherited his father Geoffrey's lands and titles.
Geoffrey was quite a dashing figure, the Antonio Banderas of his day.