Lloyd-Mostyn was the eldest son and heir apparent of Edward Lloyd-Mostyn, 2nd Baron Mostyn. He was educated at Christ Church, Oxford. He was elected unopposed at a by-election in 1854 to succeed his father as Member of Parliament for Flintshire in 1854, a seat he held until his death in May 1861, aged only 31.[1] His son Llewellyn succeeded in the barony in 1884.
^Craig, F. W. S. (1989) [1977]. British parliamentary election results 1832–1885 (2nd ed.). Chichester: Parliamentary Research Services. p. 525. ISBN0-900178-26-4.