William IV was king of the United Kingdom of Great Britain and Ireland and of Hanover from 1830 until his death. The third son of George III and younger brother and successor to George IV, he was the last king and penultimate monarch of Britain's House of Hanover. He served in the Royal Navy in his youth and was, both during his reign and afterwards, nicknamed the 'Sailor King'. He served in North America and the Caribbean, but saw little actual fighting. He inherited the throne when he was 64 years old and his reign saw several reforms: the Poor Law was updated, child labour restricted, slavery abolished in nearly all the British Empire and the Reform Act of 1832 refashioned the British electoral system. Though William did not engage in politics as much as his brother or his father, he was the last monarch to appoint a Prime Minister contrary to the will of Parliament.