In 1254 , English fears of a Castilian invasion of the English province of Gascony induced Edward 's father to arrange a politically expedient marriage between his fourteen-year-old son and Eleanor , the half-sister of King Alfonso X of Castile .
In 1254 , English fears of a Castilian invasion of the English province of Gascony induced Edward 's father to arrange a marriage between his fourteen-year-old son and Eleanor , the half-sister of King Alfonso X of Castile .