Lord Castlereagh (1769-1822) remains one of the most complex and controversial figures in modern Irish history. Frequently described as cold and aloof, he was an unpopular politician and his elusive character was little understood. As Chief Secretary for Ireland he played a major role in crushing the 1798 rebellion and passing the Act of Union (1800), but his reputation never recovered form the allegations of corruption and brutality that accompanied his time in office. Moving to Westminster after the Union, he forged one of the most impressive political careers of the early nineteenth century. As Foreign Secretary he was one of the key negotiators at the Congress of Vienna (1815), and he was hailed in Europe as one of the greatest diplomats of the age. Nevertheless, he continued to be reviled in Ireland and Britain for his association with repressive and authoritarian measures. He died in 1822 when a tragic mental collapse brought an end to one of the most distinguished and divisive political careers in Irish history.