Rhun Iorwerth was voted first minister of Wales on Tuesday, completing a political turnover that ended 100 years of Labour hegemony in the country and put Plaid Cymru in charge of a Senedd that no longer belongs to one dominant party.

Iorwerth was confirmed after a plenary vote in the Senedd, with support from 43 Plaid Cymru members and two Greens. Welsh Labour and the sole Liberal Democrat in the Siambr abstained, while Reform UK’s Dan Thomas and Conservative leader Darren Millar also put their names forward for the post.

The result followed last week’s election, when Plaid Cymru won the most seats in the newly expanded 96-seat parliament. Under Wales’s new electoral system, at least 49 seats are needed for a majority, and no party was expected to clear that bar. Plaid Cymru’s victory left it in position to form a minority government, with Reform UK taking 34 seats, Labour nine, the Conservatives seven, the Liberal Democrats one and the Green party gaining two MSs for the first time.

The day began with another change at the top of the chamber. Before the first minister vote could take place, the Senedd chose Huw Irranca-Davies as the new llywydd and elected Kerry Ferguson deputy presiding officer. Then the chamber turned to the contest for first minister, where Iorwerth secured the numbers he needed.

In his acceptance speech, Iorwerth called the victory “the greatest privilege of my life to be elected first minister in a nation that means so much to me.” He said “something has stirred in the soul of Wales – a new confidence, a new hope, a new broader horizon, never to be narrowed again by the naysayers with other priorities in other places,” and promised to lead “without prejudice or presumption,” adding that he would never take the office for granted.

He also paid tribute to Eluned Morgan, who lost her seat in the election, saying she had governed “with resilience and determination” and had “steered her government with enthusiasm and with pride at all times.” Her defeat marked the end of Labour’s hold on the top office, and Ken Skates has taken over as interim leader of Welsh Labour.

Dan Thomas, who said Reform would be “a robust opposition,” used his speech to underline the split now facing the new parliament. “I would like to remind Plaid Cymru that this chamber has a pro-union majority … The future of a prosperous Wales lies within a successful United Kingdom and Reform will ensure that that union prevails,” he said. “The people of Wales made that clear at the ballot box and Reform serves the people of Wales.”

Iorwerth now leads a government that must negotiate rather than command. He has previously said he would seek mature cooperation from opposition parties on a case-by-case basis, and his administration is expected to press the UK government for extra powers over policy areas such as policing and justice. Plaid Cymru has also ruled out an independence referendum in the next Senedd term, setting the limits of the mandate that brought it to power. The election ended Labour’s century-long grip on Welsh government, but the harder task starts now: proving that a party that won the most seats can still make a fragmented parliament govern.