source : http://www.royal.gov.uk/
Though charming, attractive and (when required) a brave warrior, Stephen (reigned 1135-54) lacked ruthlessness and failed to inspire loyalty. He could neither control his friends nor subdue his enemies, despite the support of his brother Henry of Blois (Bishop of Winchester) and his able wife Matilda of Boulogne.
Henry I's daughter Matilda invaded England in 1139 to claim the throne, and the country was plunged into civil war. Although anarchy never spread over the whole country, local feuds were pursued under the cover of the civil war; the bond between the King and the nobles broke down, and senior figures (including Stephen's brother Henry) freely changed allegiances as it suited them.
In 1141, Stephen was captured at Lincoln and his defeat seemed certain. However, Matilda's arrogant behaviour antagonised even her own supporters (Angevins), and Stephen was released in exchange for her captured ally and illegitimate half-brother, Earl Robert of Gloucester. After the latter's death in 1147, Matilda retired to Normandy (which her husband, the Count of Anjou had conquered) in 1148.
Stephen's throne was still disputed. Matilda's eldest son, Henry, who had been given Normandy by his father in 1150 and who had married the heiress Eleanor Duchess of Aquitaine, invaded England in 1149 and again in 1153.
Stephen fought stubbornly against Henry; Stephen even attempted to ensure his son Eustace's succession by having him crowned in Stephen's own lifetime.
The Church refused (having quarrelled with the king some years previously); Eustace's death later in 1153 helped lead to a negotiated peace (the treaty of Wallingford) under which Henry would inherit the throne after Stephen's death.