The only Liberal Democrat in the Senedd, Education Secretary Kirsty Williams, has triggered Conservative claims that cabinet responsibility is now in 'chaos'. She voted with Plaid Cymru and against her Labour colleagues at the end of a debate on Brexit.
Kirsty Williams voted with Plaid Cymru to oppose triggering Article 50 unless the UK government guaranteed future participation in the European Single Market. Labour AMs were whipped to vote against and the First Minister argued that it would be wrong to object to the Brexit talks getting underway following the result of the EU referendum.
Carwyn Jones had warned Kirsty Williams that she was bound by collective responsibility in a formal letter he sent her after her appointment last May.
Andrew RT Davies contrasted Kirsty Williams' survival in the Welsh Cabinet with the situation at Westminster, where former shadow Welsh Secretary Jo Stevens resigned from the Shadow Cabinet because she wouldn't toe the line on Brexit.
Despite her rebellion, Kirsty Williams says she supports the Welsh Government's position on Brexit, set out in a White Paper agreed with Plaid Cymru. She went further than the First Minister would have liked but survives because in the end her vote was a criticism of Theresa May's government, not the government she serves in under Carwyn Jones.