On 10 April 1991, the Plaid Cymru-Green alliance was officially sealed at a signing ceremony at the Porth Hotel, Llandysul. The agreement, dubbed the Llandysul Accord, established a joint electoral ticket between Plaid Cymru and the Wales Green Party for the 1992 general election.

The document, titled the “Candidate’s Undertaking”, was presented by Plaid Cymru president Dafydd Elis Thomas and Alun Williams of the Wales Green Party.

One year later, Cynog Dafis was elected as the MP for Ceredigion and Pembroke North on a joint Plaid-Green ticket. His victory marked the first occasion on which a candidate representing the Green Party was elected to the House of Commons.

Dafis reportedly “took every opportunity to announce the fact of the election of the UK’s first Green Party MP”. He later acknowledged that the distinction of being the first Green MP properly belonged to Caroline Lucas, following her election for Brighton Pavilion in 2010.

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The Llandysul Accord was a response, in part, to the 1989 European Parliament elections.

The continental contest represented a significant breakthrough for the Greens. The environmentalist party, standing a full slate of 79 candidates, won 2,292,695 votes (14.5%) – the highest share ever won by any European Green party in a national contest at that time. The Greens placed third overall, polled over 20% in 17 constituencies and outperformed the Social and Liberal Democrats (soon to be rebranded as the Liberal Democrats) in all but one seat. The Greens surpassed the SLD nationally.

Notably, the strong Green performance pushed Plaid Cymru into fourth place in several Welsh constituencies.

The ideological roots of the Plaid-Green alliance were provided by the parties’ shared decentralist philosophy and opposition to untrammelled economic growth. Dafis, a former schoolteacher and Welsh nationalist, viewed the small nation and local community as the essential units for a sustainable economy.

In his 2005 Welsh Political Archive annual lecture on Plaid-Green cooperation, Dafis said he was inspired by Edward Goldsmith’s A Blueprint for Survival (January 1972). This influential tract helped spark the creation of the environmentalist PEOPLE party in February 1973, which successively rebranded as the Ecology Party (in 1975) and the Green Party (1985).

However, the formation of a Plaid-Green alliance also faced resistance on ideological grounds.

Cith ap Henri resigned from the Plaid Cymru executive committee in March 1990, dismissing the Greens as a “party of cranks, the vegans, wigwam dwellers, the visionaries and the ardent middle-class good-lifers”.

They added: “We have heard a great deal about the need to change Plaid Cymru’s policy in order to accommodate them. We have heard nothing about the Greens being converted to the campaign for a Welsh national state.”

Royston Jones, a member of the fundamentalist Covenant Society of the Free Welsh, issued a visceral written attack on Dafis, labelling him and his associates as “ugly little bloodsuckers on the long-suffering body of our people” for seeking “to share the feast with other, English parasites”.

Conversely, a Green fundamentalist (or fundi) tendency opposed any accommodation with nationalism, citing its perceived incompatibility with environmentalist politics. Dafis faced a “ferocious attack” on these grounds when he appeared at the 1991 Green Party conference in Wolverhampton. Chris Busby, a Green member, was reportedly outraged that community councils in Gwynedd conducted their business in Welsh.

By early 1991, however, a Plaid-Green pact had been endorsed overwhelmingly by both parties – in time for an unexpected by-election in Monmouth. In the spirit of cooperation, Plaid supported the Green candidate in Monmouth, Melvin Witherden, who polled only 277 votes (0.6%).

Witherden placed fifth, finishing behind Screaming Lord Sutch and the Monster Raving Looney Party (314).

Despite this, the official Plaid-Green compact was signed at the Porth Hotel, Llandysul, on 10 April 1991. The official Candidate’s Undertaking committed representatives of both parties to a joint campaign and a shared parliamentary programme built around environmentalism.

The joint campaign, operating under the slogan Gyda’n Gilydd – Working Together, stood in seven seats at the 1992 general election and secured a decisive victory for Dafis in Ceredigion and Pembroke North.

Dafis won 16,020 votes (31.3%), a 15 point increase from his 1987 performance, defeating the incumbent Liberal Democrat with a majority of 3,193. The combined Plaid-Green vote share at the 1987 general election was 8,669 (17.9%).

Ceredigion and Pembroke North was the only seat at the 1992 general election in which a candidate rose from fourth place to victory. And the 13.3 point swing from Lib Dem to Plaid Cymru-Green was the highest in the country.

Jonathon Porritt, the leading Green organiser and onetime chair of the predecessor Ecology Party, was among those who campaigned alongside Dafis in Ceredigion and Pembroke North. He spoke at a packed meeting in the Old College Hall, Aberystwyth, shortly before the poll.

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In his maiden speech, delivered to the commons on 11 May, Dafis acknowledged his Green roots. He looked ahead to the upcoming “Earth Summit” in Brazil, with 108 heads of state and government planning to attend. Dafis predicted that the “measures likely to be taken by that conference in Rio will fall far short of what is necessary to save our planet.”

He added: “I do not think that I am using overly dramatic language when I use words such as ‘to save our planet’.”

Dafis singled out the “thoroughly irresponsible behaviour” of the United States, “which, with 5% of the world’s population, is responsible for 25% of the world’s CO2 emissions.”

Dafis also argued that while economic growth is needed for the “poor peoples of the world”, it must be “sustainable in terms of the natural systems that make life possible or, at the very least, tolerable on planet earth.” He linked the “terrible drought in southern Africa” to the phenomenon of global warming, warning that current CO2 levels are “in all probability, unsustainable and may very well be causing deadly damage now.”

Dafis called for the prime minister, John Major, to go to Rio with a commitment to “reduce unilaterally and significantly CO2 emissions in Britain.” He said this would require a massive shift from fossil fuels to “non-polluting renewable sources such as wind, tide, wave and hydro.”

Speaking at the intersection of his Welsh nationalism and sustainability, Dafis lamented that Wales had historically seen its resources, such as “water and opencast coal mining”, extracted for the “financial benefit of powerful external forces”.

Dafis concluded by declaring: “It is my conviction that the establishment of a democratic parliament for Wales is the only satisfactory way to provide the right economic and social development for our country.”

The parliamentary work of the Plaid-Green MP was greatly aided by researcher Victor Anderson, an economist and Green member, and Ron Bailey, the Green Party’s national campaigns coordinator.

Dafis became a focus for Green campaigns, successfully promoting the Energy Conservation Bill, which he introduced under the 10-minute rule in 1993. The bill, which was picked up by the Liberal Democrats, eventually reached the statute book as the Home Energy Conservation Act 1995.

Dafis also championed the Road Traffic Reduction Bill (later act), which he introduced under the 10-minute rule in 1995, and served as an inaugural member of the House of Commons environmental audit committee.

Dafis later remarked that he was “acting as an instrument for the Green Party and the green movement in parliament.”

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The Plaid-Green alliance was ultimately short-lived, however.

Dafis’ breakthrough came at a moment when the fortunes of the Green Party of England and Wales were otherwise in decline.

The Green Party entered the 1992 general election at a time of internal strife. A faction known as Green 2000 had succeeded in streamlining the party’s governance, but its push towards a more conventional leadership structure provoked fierce opposition from members committed to decentralisation. Between 1990 and 1992, the party lost more than half its membership, a decline of some 5,500 members. The situation was further compounded by the revelation that one of the party’s leading spokespeople, David Icke, was a conspiracy theorist.

In August 1992, Sara Parkin, who had come to national attention during the 1989 European Parliament elections as a leading Green spokesperson, announced her intention to step down. In her resignation letter, Parkin wrote that she saw “no point in squandering my time, energy and spirit fighting endless redundant skirmishes behind the Green Party barricades”, and that she had been “forced to the conclusion that the Green Party is a liability to green politics.”

The Greens and Plaid Cymru could not come to an arrangement in time for the 1994 European Parliament elections. Rather, Chris Busby – an implacable Green opponent of the pact – was selected as the Green candidate for Mid and West Wales.

Busby’s selection symbolised the growing opposition to the accord among Welsh Greens.

Dafis responded by soliciting an endorsement from Jonathon Porritt for the Plaid Cymru candidate in Mid and West Wales. The Green Party Regional Committee (of which Chris Busby was a member) retaliated by suspending Porritt and demanding that Dafis cease describing himself as a Plaid Cymru-Green MP.

Porritt responded in an article for the Independent newspaper, published on 29 August 1994. He ridiculed those in the Green Party who wanted to “take on the task of Keeper of the Holy Green Grail, defining with involuntary arrogance what is or is not truly green.”

Porritt wrote: “By a process of remorseless exclusion, just about the only thing that is left is its own navel.”

By July 1995, with suspicions growing on both sides, the Plaid-Green pact was formally dissolved at a press conference at the Talbot Hotel. In a defiant joint statement, the parties celebrated five years of progressive cooperation, but conceded that the “destructive energies of an unrepresentative minority” had made the arrangement untenable.

Dafis contested the 1997 election solely as a Plaid Cymru candidate, returning to parliament with 16,728 votes (41.6%). The Greens only stood in 95 candidates at the 1997 election, and did not contest Ceredigion.

Dafis stood down as an MP in January 2000 to concentrate on his work in the Welsh Assembly, which he had won election to in 1999 as part of its inaugural cohort. A commons early day motion (EDM), signed by 24 MPs including Jeremy Corbyn and John McDonnell, paid tribute to Dafis’ work “in the fields of world and UK sustainable development”.

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At the 2010 general election, Caroline Lucas, the leader of the Green Party of England and Wales (GPEW), was elected as the MP for Brighton Pavilion, securing a majority of 1,252.

Upon meeting Dafis in 2011, he graciously relinquished any claim to her title, declaring: “I was a kind of hybrid, so I don’t really count. I am more than happy to say that Caroline Lucas is the first Green MP.”

Lucas paid fulsome tribute to Dafis as a “legend”, stating: “He’s legendary in the green movement and it is an honour to actually meet him here today.”

Despite the Llandysul Accord’s short lifespan, the Green Party and Plaid Cymru have remained among the parties most receptive to alliances and electoral pacts.

At the 2019 general election, the Greens and Plaid Cymru, together with the Liberal Democrats, embraced a limited (anti-Brexit) election pact that saw the parties stand aside in dozens of constituencies to boost their partners’ chances. The deal covered 60 constituencies across England and Wales.

Of the 60 constituencies, 10 had Green candidates only, including Brighton Pavilion, Bristol West, Bury St Edmunds, Cannock Chase and Vale of Glamorgan.

This followed the Brecon and Radnorshire by-election in August 2019, which saw the Greens and Plaid Cymru stand aside in favour of the Liberal Democrats. Jane Dodds, the Lib Dem candidate, narrowly defeated the Conservative candidate by 1,425 votes.

In September 2021, the spirit of the earlier Plaid-Green accord was revived with the formation of the Common Ground Alliance – an electoral pact for Cardiff Council elections.

A total of 46 Plaid and 24 Green candidates stood under the alliance banner in the May 2022 local elections. The collective professed to bring “a new kind of politics to Cardiff”.

Common Ground ultimately won 17% of the vote and two seats.

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The Wales Green Party won seats in Senedd Cymru for the first time in the May 2026 elections. Both Green MSs, Paul Rock and Anthony Slaughter, supported Plaid Cymru leader Rhun ap Ioworth in his elevation as first minister of Wales.

Slaughter, the leader of the Wales Green Party, described Plaid Cymru’s performance in the May 2026 Senedd elections as “good for Welsh politics”.