His first months at the Welsh Office were difficult despite the fact that Labour had won 32 of the 36 Welsh constituencies. On 14 July 1966, Gwynfor Evans won the Carmarthen by-election to become the first Plaid Cymru MP leading to an upsurge in support for political nationalism, which was also reflected in the Welsh Language Society's active campaign for bilingual road tax licences. Within the Labour Party a minority of Welsh MPs and activists supported some form of devolution reminiscent of the campaign which Hughes had supported in the 1950s. At the same time many of Hughes's Labour colleagues, particularly veteran MPs in the industrial south, were fiercely opposed to any form of devolution. Hughes ended up caught between these two wings, and disappointed those who had anticipated a greater move towards devolution. In 1968 Hughes was succeeded as Secretary of State by George Thomas, whose views on the subject were fundamentally opposed to those of his predecessor.