The First Ministers of Wales and Scotland have joined forces to urge the Prime Minister to think again about her position on Britain's future trading relationship with the European Union.
In their joint statement, Carwyn Jones and Nicola Sturgeon say the UK should remain in the EU single market and customs union.
The UK Government's official position is that Britain will leave both when it leaves the EU.
The Welsh and Scottish First Ministers have made their call ahead of a meeting of leaders and ministers from the different governments of the British Isles on Guernsey.
Ahead of the same meeting, the UK Government has promised to maintain good working relationships with devolved governments despite the 'political noise' of Brexit.
The two First Ministers say the Prime Minister should use her long-promised White Paper to commit to keeping Britain within the Single Market and Customs Union in what they call a 'Norway Plus' relationship with the EU.
The gathering on Guernsey will be the 30th meeting of the British Irish Council which brings together the UK and Irish Governments along with Welsh and Scottish First Ministers and leaders of Isle of Man, Jersey and Guernsey. Northern Ireland's devolved government remains suspended.
The Irish Taoiseach, Leo Varadkar, will be present while the UK Government's representative will be the Cabinet Office minister David Lidington.
Carwyn Jones and Nicola Sturgeon may be united in their opposition to the UK Government's approach to Brexit but their partnership in another area of conflict has ended.
They had been battling the effects on devolution of the Withdrawal Bill, something they both described as a 'power grab.'
But while the Welsh Government accepted a compromise and gave its grudging approval to the bill, Scottish ministers remained opposed which means its changes will be implemented despite its rejection by the Scottish parliament.
That might explain this conciliatory and Scotland-focussed statement made ahead of the meeting by David Lidington: