Born Robyn Lewis, he studied at Pwllheli Grammar School and University College of Wales, Aberystwyth before becoming a solicitor and barrister. He became active in the Labour Party and stood, unsuccessfully, in Denbigh at the 1955 general election.
During the 1960s, Léwis left Labour and joined Plaid Cymru. He was elected to Lleyn Rural District Council, and stood for the party in Caernarfon at the 1970 general election, where he came second with more than 33% of the vote. He was subsequently elected as a Vice President of Plaid.
In 1980, Léwis won the Prose Medal at the National Eisteddfod of Wales, and in 2002 he was the first Prose Medallist to become Archdruid, under the title "Robyn Llŷn". In this role, he inducted future Archbishop of Canterbury Rowan Williams as a Bard of the Gorsedd.
- The Times Guide to the House of Commons 1970, p.71
- "Dr Robyn Lewis: I'm willing to return to Plaid Cymru", North Wales Daily Post, 18 August 2008
- "Prose Medal Archived 2014-10-30 at the Wayback Machine", National Eisteddfod of Wales
- "Archdderwydd". Gorsedd y Beirdd (in Welsh). Retrieved 20 September 2016.
- Marcus Tanner, The Last of the Celts, p.189
|Party political offices|
| Vice President of Plaid Cymru
| Archdruid of the National Eisteddfod of Wales