On the death of his father on 5 November 1806, Ponsonby succeeded him as
Baron Ponsonby, and for some time held an appointment in the
Ionian Islands. On 28 February 1826, he went to
Buenos Aires as
envoy-extraordinary and minister-plenipotentiary until 1828, and moved then to
Rio de Janeiro in the same capacity. An exceptionally handsome man, he was sent, it was reported, to South America by
George Canning to please
King George IV, who was envious of the attention paid him by
Lady Conyngham. Once there he greatly fostered the independence of
Uruguay as a
buffer state between
Argentina and
Brazil, to the benefit of British commerce and overall peace. In December 1830 he was entrusted with a special mission to
Belgium, in connection with the candidature of
Prince Leopold of Saxe-Coburg to the Belgian throne, and remained in Brussels until Leopold was elected king on 4 June 1831. His dealings in this matter were adversely criticised in
The Guet-à-Pens Diplomacy, or Lord Ponsonby at Brussels, … London, 1831, but the Prime Minister,
Lord Grey, eulogised him in the
House of Lords on 25 June 1831. Thus, as a diplomat, he was sent twice by the
British Empire to promote the instauration of buffer states to protect its interests, Uruguay and Belgium, both of which survive to this very day, still deeply similar to their bigger neighbours. In addition to this, Ponsonby served as envoy to
Naples from 8 June to 9 November 1832, as ambassador at
Constantinople from 27 November 1832 to 1841, and as ambassador at
Vienna from 10 August 1846 to 31 May 1850. ==Later life==