Complex sentence: Margaret of Anjou (23 March 1430--25 August 1482) was the Queen of England by marriage to King Henry VI of England from 1445 to 1461 and again from 1470 to 1471.
Split into simpler sentences: Margaret of Anjou (23 March 1430--25 August 1482) was the wife of King Henry VI of England. As such, she was Queen of England from 1445 to 1461 and again from 1470 to 1471.