High Quality Content by WIKIPEDIA articles! Thomas Pelham-Holles, 1st Duke of Newcastle-upon-Tyne and 1st Duke of Newcastle-under-Lyne, KG, PC (21 July 1693 17 November 1768) was a British Whig statesman, whose official life extended throughout the Whig supremacy of the 18th century. He is commonly known as the Duke of Newcastle. A protege of Sir Robert Walpole, he served under him for more than twenty years until 1742. He held power with his brother, Henry Pelham (the Prime Minister of Great Britain), until 1754. He had at this point served as a Secretary of State continuously for thirty years - dominating British foreign policy. After Henry's death, the Duke would hold his late brother's position for six years (in two separate periods). While his first premiership was not particularly notable, Newcastle precipitated the Seven Years War, which would cause his resignation from his high position. After his second term as Prime Minister, he served for a short while in Lord Rockingham's ministry, before retiring from government.