Born in Machen in the Rhymney Valley in Monmouthshire, he was educated in Bassaleg Grammar School before graduating in Geography at Portsmouth Polytechnic.

[3] After two years as a backbench MP, Davies was appointed an Opposition Whip in 1985, where his subject areas included agriculture and the environment.

In 1987 he was appointed to the opposition frontbench as a spokesman on Agriculture and Rural Affairs responsible for reviewing the Labour Party's policies on animal welfare.

He negotiated support for a sixty-member Welsh Assembly to take over the functions of the Secretary of State for Wales and elected by an element of proportionality.

One of his first acts was to return the £150,000 to the Aberfan disaster fund that a previous Labour Government had taken to restore the site of the landslide that had devastated the valley's community in 1966, although controversially this was without interest being paid.

He has been credited with being "the architect of devolution", and was appointed to the highest order of the Gorsedd of the Bards at the 1998 National Eisteddfod in Bridgend, earning the bardic name "Ron o Fachen" (Ron from Machen) On 19 September 1998, Davies defeated Rhodri Morgan to become Labour's candidate for First Secretary of the Assembly at a special Welsh Labour Party conference in Newport.

He stood down citing "an error of judgement" in agreeing to go for what he said was a meal with a man he had met while walking on Clapham Common in London, which is a well-known gay meeting place.

The full details of the incident (which he infamously called a "moment of madness" at the urging of Tony Blair's Press secretary Alastair Campbell) have never emerged.

He was elected on 6 May 1999 as Assembly Member for the Caerphilly constituency, and initially chaired the Economic Development Committee after Alun Michael refused to appoint him to his Cabinet.

He is known for the phrase "Devolution is a process and not an event", by which he meant that the settlement he introduced in 1997 would not be the final one, and more powers would accrue to the Welsh Assembly over time.