• 1912: He starts preaching.
• 1913: He went to the University College of North Wales, Bangor.
• 1916: Valentine joined the Royal Army Medical Corps (RAMC) and arrived in France at the end of September.
• 1917: He is seriously wounded on 23 October when he inhaled poisonous gas whilst treating the wounded at the battle of Passchendaele.
• 1925: Plaid Genedlaethol Cymru (The National Party of Wales) was established, and Valentine was elected as president.
• 1929: Valentine was the Party’s first parliamentary candidate when he stood for the Caernarfonshire constituency at the general election.
• 1936: September – He burnt the Bombing School with Saunders Lewis and D. J. Williams.
• 1947: He became the minister of Penuel chapel in Rhosllanerchrugog.
• 1951: He became editor of ‘Seren Gomer’.
• 1970: He retired from the Ministry.
• 1986: The University of Wales awarded him an honorary doctorate in Divinity, but he did not live to receive it.
‘Should we mention the bombing school in Llŷn and Wormwood Scrubs? But it was respect for Wales and his fellow Welshmen that brought Mr Valentine to that crisis, and that was consistent with his whole attitude towards his congregation in his chapel, his denomination and his country.’ – Translated from Saunders Lewis, ‘Seren Cymru’ (1971) in Arwel Vittle, ‘Valentine: Cofiant i Lewis Valentine’ (Y Lolfa 2006), p. 10