After leaving school aged 12 and working for some years in local pits, Davies studied mining engineering and later took an Arts degree at University College, Cardiff.

[3][4][n 1] His birthplace was 39 John Street, Abercwmboi (then known as Cap Coch) in the South Wales coalfields,[5] the fourth child of Thomas Davies and his wife Esther (née Owen).

[1] Thomas was a miner and trade union activist, who under the pseudonym Y Llwynog ("the Fox") wrote a column for the Welsh language newspaper Tarian y Gweithiwr ("The Worker's Shield"), in which he berated pit management and safety practices.

[6][7] Davies attended the local Cap Coch school, leaving at the age of 12, as was usual at that time,[n 2] to begin work in the Cwmpennar coal mine.

His ambition and intelligence were quickly recognised by his superiors, and he was encouraged to study mining engineering, at first locally in Aberdare and, in 1907, at the Royal College of Science in London.

His plans to enter the ministry were abandoned; he was an active member of the Independent Labour Party (ILP), and his religious vocation had been replaced by a commitment to working-class politics.

The main role of the agent was to represent miners in disputes with their employers; typically these would involve issues of pay, redundancy, working hours, and compensation for injuries.

[4] The years following the First World War saw economic decline and hardship in the South Wales coalfields, conditions which deepened Davies's radical instincts, and he began to acquire a reputation for militancy.

When the national strike collapsed after nine days, Davies led the continued resistance from the Welsh coalfields through months of lockout, before capitulation on harsh terms in December.

Davies and other non-communists found themselves accused of collaboration with "social fascism"; a leaflet issued by the communist-led National Minority Movement termed him "the sham militant".

[2] When Richard Wallhead, the Labour MP for Merthyr, died on 27 April 1934,[21] Davies was selected as the party's candidate for the June by-election, with the support of the MFGB.

[24][n 6] With no candidate from the ruling National Government in the field, Davies was denied an obvious target for attack; as The Manchester Guardian stated in its pre-poll analysis, he was put on the defensive: "His is the dispiriting task of trying to lose as few votes as possible".

[24] Using the slogan "Peace, Prosperity, Security, Freedom", Davies advocated the extension of public ownership, abolition of the means test, increased unemployment benefit, better education, and international co-operation especially with Russia.

[2][43] Stating his position in a 1948 letter to the Labour Party general secretary Morgan Phillips, he wrote: "Our movement embraces millions of men and women, and not merely a few hundred MPs and a few dozen ... members of the National Executive.

[44] In June 1953 he was attacked by Will Lawther, the NUM president, for defying the Labour Party's position and supporting the Soviet claim that a workers' rising in East Germany had been orchestrated by "a CIA-sponsored West-German pro-fascist organisation".

[49] Davies persevered, and on 4 March 1955 introduced in the House of Commons a private member's bill proposing self-government for Wales on the basis of the aborted 1914 act that would have granted home rule to Ireland.

"[52] According to Griffiths, when Soviet troops suppressed the Hungarian uprising in October 1956, Davies was troubled, but refused to join in the general censure lest this give comfort to the enemies of socialism.

He was to be equally silent during and after the events of the Prague Spring of 1968[53]—in sharp contrast to his condemnation of the "criminally dangerous and irresponsible heroics" of the United States during the Cuban Missile Crisis of October 1962.

[56] In the immediate aftermath, Davies visited and consoled the bereaved families in Aberfan, and the following day he led a party which included the Duke of Edinburgh on a tour of the disaster site.

[61] His testimony was strongly challenged by the NUM, whose counsel Brian Gibbens QC said that "[i]f Mr Davies is to be accepted as truthful and accurate in his recollection ... then he bears what must be one of the largest personal burdens of responsibility for the disaster".

[63] The tribunal's findings, published in July 1967, placed responsibility for the disaster firmly on the National Coal Board, specifically on the absence of any tipping policy.

[75] Friends advised him not to risk humiliation; no deselected candidate in recent times had won election against the party machine, and Davies would, they predicted, get no more than 1,000 votes.

They chose Tal Lloyd, an Amalgamated Engineering Union (AEU) official, a long-serving councillor and a former mayor, on the moderate wing of the Labour Party, and a strong supporter of Wilson.

[78] As polling day approached, however, it was clear that he was gathering support, particularly among the young—a great irony, Alun Morgan observes, for a man sacked on the grounds of his age.

[79] In the final week before polling day on 18 June Davies's youthful supporters toured the constituency with songs, slogans and cheerleaders in what Griffiths describes as "the most colourful election bandwaggon seen in Merthyr for 40 years".

[80] The official Labour campaign stalled, as Lloyd became embroiled in a row over his role in the failure of the AEU to support an unofficial strike at the local Hoover factory.

[83] Despite his expulsion, in July 1970 the Labour-controlled Merthyr council offered Davies the freedom of the borough, an honour which he politely declined; the confidence of the people recently shown him was, he said, enough.

Griffiths records: "It was indicative of [Davies's] breadth of vision that the ceremony attracted socialists, communists, Welsh nationalists, republicans, and many of no political creed at all".

[89] In the April by-election to fill the vacancy caused by Davies's death the Labour candidate, Ted Rowlands, won the seat with a narrow majority over Plaid Cymru.

[90] According to a BBC correspondent, Davies "looked as if he belonged to a different age, in his parliamentary 'uniform' of homburg hat, silk scarf, black jacket and pin-striped trousers".