Reform's Welsh leader arrested and deputy defects as party endures its most 'challenging' week yet

From the Newshound archive · first published 20 September 2026.

Reform UK's Welsh leader Dan Thomas stepped down after being arrested on suspicion of assault and controlling or coercive behaviour, then bailed, in a crisis his Senedd colleagues only heard about after it had unfolded. Thomas had initially absented himself from First Minister's Questions, giving "personal reasons" as his explanation, but a WhatsApp message to fellow members ultimately pushed him to act. The situation worsened within days once the arrest became public knowledge and a Reform Senedd member defected to Plaid Cymru. Llŷr Powell, Reform's chief whip in the Senedd, conceded it had been a "challenging" week while insisting the party had "come through it".

Thomas, who remains a Reform MS for Casnewydd Islwyn, told media he had "done nothing wrong" and was "released without charge".

The turmoil lands as a fresh Ipsos poll puts Labour four points ahead of Reform, with six in ten voters saying the party is not ready for government.

Robert Jenrick used a Sun on Sunday column to pledge Reform would deploy AI to "wage war on benefit cheats" — a bid to keep the policy agenda alive amid the Welsh chaos.