Of perhaps greater significance, however, was the impetus the episode gave to Welsh devolution. The Council of Wales recommended the creation of a Welsh Office (Swyddfa Gymreig) and a Secretary of State for Wales early in 1957, a time when the governance of Wales on a national level was so demonstrably lacking in many people's eyes. The flooding of Capel Celyn also sharpened debate within Plaid Cymru about the use of direct action. While the party emphasised its constitutional approach to stopping the development, it also sympathised with the actions of two party members who (of their own accord) attempted to sabotage the power supply at the site of the Tryweryn dam in 1962. In October 1965 the Llyn Celyn reservoir opened to a sizeable Plaid Cymru organised demonstration. During the opening ceremonies, "posters reading 'Hands Off Wales' were displayed and pieces of rock were thrown at Liverpool's Lord Mayor and Chief Constable." In 2005, the Liverpool City Council formally apologised for the flooding. Tynged yr Iaith and the 1961 census See also Tynged yr iaith. In 1962 Saunders Lewis gave a radio speech entitled Tynged yr iaith (The Fate of the Language) in which he predicted the extinction of the Welsh language unless action was taken. Lewis' intent was to motivate Plaid Cymru into more direct action promoting the language; however it led to the formation of Cymdeithas yr Iaith Gymraeg (the "Welsh Language Society") later that year at a Plaid Cymru summer school held in Pontardawe in Glamorgan. The foundation of Cymdeithas yr Iaith Gymraeg allowed Plaid Cymru to focus on electoral politics, while the Cymdeithas focused on promoting the language. Lewis gave his radio speech responding to the 1961 census, which showed a decrease in the number of Welsh speakers from 36% in 1931 to 26%, out of a population of about 2.5 million. In the census; Merionnydd, Ynys Môn, Carmarthen, and Caernarfonshire averaged 75% concentration of Welsh speakers, with the most significant decrease in the counties of Glamorgan, Flint, and Pembroke. Responding to the calls for Welsh devolution, in 1964 the Labour Government gave effect to these proposals establishing the unelected Welsh Office () and a Secretary of State for Wales. Evans' election 1966 If Plaid Cymru had been disappointed at the UK general election, 1966, then the Carmarthen by-election of 14 July 1966 was reason for celebration. The contest was significant in that it resulted