Glyn James: Plaid Cymru leader in the Rhondda Valley and pioneer of Radio Free Wales

Television viewers in Wales during the late 1950s were able to tune in to an extra radio programme after the closedown of the BBC service around 11 o'clock.

As the signal faded, they would hear: "Do not switch off. Do not switch off. You are listening to the voice of Free Wales". There followed a mix of news, interviews and folksongs that ended with the Welsh national anthem and sometimes "Men of Harlech". The man behind this daring initiative, which predated Radio Caroline, was Glyn James, a prominent Welsh Nationalist and stalwart of Plaid Cymru in the Rhondda Valley.

The pirate radio was started after Plaid Cymru was banned by Charles Hill, the Postmaster General, from making party political broadcasts and thus found itself at a disadvantagein the electoral fray that was justhotting up in Wales. The radio was run by a small group of Nationalistswho had built their transmitter on advice from members of the Scottish National Party. This contraption had a range of only a few miles but the wheeze received widespread publicity and contributed to a sense of national resurgence. The transmitter was moved from place to place and none of the broadcasters, who included Plaid Cymru's president Gwynfor Evans, Carwyn James the rugby player, Rhydwen Williams the writer, Ray Smith the actor and Harri Webb the poet, was ever brought to book. Eventually, Plaid Cymru was allowed air-time, after which Radio Free Wales entered the annals of Welsh Nationalist legend.

I once played a small part in oneof these clandestine broadcasts which took place in the attic of Garth Newydd, a rambling old house in Merthyr Tydfil where I lived in a commune with other Plaid activists. My job was to listen for any knock on the door and, sure enough, it came: it was the local bobby on his late-night beat, calling as he often did for a chat and cigarette. Fortunately, Glyn James and Harri Webb had also heard the knock, and down they came into the living-room to find me in nervous conversation with the caller. I made them all a pot of tea and the policeman was kept in pleasant conversation with Glyn and Harri for more than an hour while the conspirators upstairs made illegal use of the airwaves. None of us was cooler than Glyn James who used his immense charm to entertain the unexpected caller with an assortment of stories and jokes.

Within the year Glyn had become a part-time organiser for Plaid Cymru in south-east Wales, which was always the area in which he felt most at home, winning many adherents to the Nationalist cause. A little later, he was elected to Rhondda Borough Council and then the Mid-Glamorgan County Council on which he served two terms (1961-64 and 1967-69); he was elected Mayor of Rhondda in 1960 and Honorary Alderman in 1991. He also stood as the party's candidate at General Elections in Rhondda constituencies on seven occasions between 1955 and 1979, a tireless campaigner whose energies never flagged.

Glyn James was a native of Llangrannog in Cardiganshire, one of the eight children of a carpenter who had worked in the Rhondda coalmines. Educated at Cardigan Grammar School and the Glamorgan Technical College in Trefforest near Pontypridd, which later metamorphosed into the University of Glamorgan, he served his apprenticeship at a foundry in Cardigan before qualifying as a mining engineer in 1942.

At the Tylorstown pit where he took his first job as a fitter he was given the task of adjusting the hooter so that local people could distinguish its wail from other pit-hooters in the Valley. He spent the rest of his life working at pits in the Rhondda, where he met Hawys Williams, daughter of a Ferndale minister, who was to become his wife. A talented guitarist, she was often to be heard singing folksongs on Radio Free Wales and was his helpmeet in all the electioneering to which he devoted his life.

Recruited by Kitchener Davies, the legendary pioneer of Plaid's cause in the Rhondda, Glyn joined the party at the age of 19 in 1944 and spoke in public for the first time at the General Election of the year following. He took part in some of the earliest extra-parliamentary Nationalist campaigns such as the unsuccessful attempt to prevent the Army building a training camp at Trawsfynydd in Merioneth, where he sat down in the road with some of Plaid Cymru's leaders. On the day the mines were nationalised in 1947, he ran up a Red Dragon to replace the Union Flag which had hitherto been flown above the pit where he worked. He also took part in demonstrations against the monarchy during the run-up to the Investiture of the Prince of Wales in 1969.

During the miners' strike of 1972 he and another county councillor were arrested for having hurled leaflets calling for 'Cyfiawnder i'r glowyr! Justice for the miners!' into the debating chamber of the House of Commons, for which they spent a night in the cells and were assaulted by the police. After 1972, when the party began to disappoint those who had hoped for an outbreak of Nationalist feeling in the industrial valleys of the south-east, Glyn James was among those who grew ever more critical of its leaders, though he continued his political activities as vigorously as before.

Although Welsh was his first language, and that of his home in Ferndale in the Rhondda Fach, he was not aligned with the militant language movement Cymdeithas yr Iaith Gymraeg, preferring to fight for jobs and investment in the valleys of south Wales. He was nevertheless active in the Welsh Schools Movement for which he was awarded the TH Parry-Williams Medal at the National Eisteddfod of 1991, one of the most prestigious honours to which a Welsh-speaking patriot can aspire. He was also made an honorary member of the Gorsedd of Bards for his services to Welsh culture in the Rhondda.

Undoubtedly one of Plaid Cymru's most flamboyant characters, Glyn had a convivial personality, a sturdy physique, a mop of flame-red hair, bushy sideburns, and a sonorous voice – he had toyed with the idea of becoming a full-time actor for radio and was a popular lay-preacher – as well asa fine flow of rhetoric in both Welsh and English. He lived to see Plaid Cymru make electoral progress in the Rhondda in the persons of younger men and women who had been inspired by him and he expressed satisfaction when the party entered coalition with Labour in the National Assembly in 2007.

Glyndwr Powell James, mining engineer, Plaid Cymru activist and pioneer of Radio Free Wales: born Llangrannog, Cardiganshire 26 March 1925; married Hawys Williams (two children); died Llwynypia, Rhondda Cynon Taf 4 December 2010.