Trench was the son of William Thomas Le Poer Trench, 3rd Earl of Clancarty and Lady Sarah Juliana Butler.
Trench was Secretary of the British Embassy in Berlin between 1888 and 1893.
He was the British Minister in Tokyo in 1894-1895.
- Ian Nish. (2004). British Envoys in Japan 1859-1972, pp. 72-77.
- Lundy, Darryl. "Power Henry Le Poer Trench, ID #48807". The Peerage.[unreliable source]
- The first British Ambassador to Japan was appointed in 1905. Before 1905, the senior British diplomat had different titles: (a) Consul-General and Envoy Extraordinary and Minister Plenipotentiary, which is a rank just below Ambassador.
- Ian Nish. (2004). British Envoys in Japan 1859-1972. Folkestone, Kent: Global Oriental. ISBN 9781901903515; OCLC 249167170