He gained the courtesy title Viscount St Asaph when his father succeeded in the earldom in 1812.
[1] He was educated at Trinity College, Cambridge, graduating MA in 1805.
[2] Ashburnham was returned to Parliament for New Romney in 1807, a seat he held until 1812,[1][3] and then represented Weobley (succeeding his uncle Lord George Thynne) until his death in 1813.
[1][4] Lord St Asaph died unmarried at Dover Street, London, in June 1813, aged only 27.
His half-brother Bertram Ashburnham eventually succeeded in the earldom.