The Magna Carta was a significant influence on the long  historical process that has resulted in the rule of constitutional  law today.    The Magna Carta came about because King John (who only became king  in 1199 when his brother King Richard I died) had a reputation for  being tyrannical. His reign was marred by continuous war losses,  beginning with the loss of Normandy to Philippe Auguste of France  and ending with England torn by civil war.