Though Robert Stewart, Viscount Castlereagh remains well known today for his role in shaping the post-Napoleonic peace settlement in Europe, his half-brother Sir Charles Stewart has received far less attention despite his own prominent part in the politics and diplomacy of those years. In War and Diplomacy in the Napoleonic Era: Sir Charles Stewart, Castlereagh and the Balance of Power in Europe
(Bloomsbury Academic, 2019), Reider Payne
describes the adventurous life of the third Marquess of Londonderry and the roles he played in the events of his time.
As a young man Charles Stewart initially pursued a career in the military rather than one in politics, and served in the cavalry during Great Britain’s war against revolutionary France in the 1790s. After a brief period in the War Office he resumed his military career and served with the Duke of Wellington in the Peninsular War. His record as an officer and his relationship with his half-brother led to his appointment as an ambassador – first to Prussia, then to Austria – in which roles he represented Britain at the courts of her most prominent allies during the final stages of the Napoleonic Wars. Though Charles was often better known for his social escapades, he served ably as Britain’s ambassador to Austria until his brother’s suicide in 1822, during which time he was active in both post-Napoleonic diplomacy and the efforts to collect incriminating evidence against Princess Caroline of Brunswick in aid of the Prince Regent’s effort to divorce her.