The Acts of Union, passed by the English and Scottish Parliaments in 1707, led to the creation of the United Kingdom of Great Britain on 1 May of that year.
William was victorious at the Battle of Hastings due to his excellent leadership skills. Harold and his army because Harold made some mistakes. William won the Battle of Hastings because of his superior strategy and tactics. William was helped to victory by Harold being unlucky on a number of occasions.
Answer: The Acts of Union and William.
Source: www.english-heritage.org.uk, www.parliament.uk