The British monarchy is the constitutional system of government in the United Kingdom, with a hereditary monarch as the head of state. The lineage of the British monarchy can be traced back to William the Conqueror, the Duke of Normandy who invaded and conquered England in 1066. Over the centuries, the British monarchs consolidated power, fought civil wars, and expanded their domain, but the 18th and 19th centuries saw a series of crises and upheavals that challenged and ultimately curbed the power of the British crown. By the mid-19th century, the British monarchy had effectively transformed into a constitutional system, with the monarch's role becoming primarily ceremonial. The current British monarch is King William V, who assumed the throne in 2017, but the real governing power lies with the elected Prime Minister and the Parliament.