What each devolved body can do

The same round of devolution legislation that set up the Scottish Parliament also covered Wales and Northern Ireland. In 1998, Parliament passed the Northern Ireland Act and the Government of Wales Act, giving each nation its own elected body with defined powers over matters such as education, health and the environment, while decisions on defence, immigration and similar national matters stayed with Westminster.

Devolution in Northern Ireland did not run smoothly at first: because power in the Northern Ireland Assembly is shared between rival parties, the UK government has had to suspend it more than once when local leaders could not work together, taking control back to Westminster in the meantime. Since 2007, though, the Assembly has kept sitting without a further suspension, a period of stability the earlier years did not have.

Wales, meanwhile, kept building on its own powers. From 2011, the Welsh Assembly no longer needed Westminster's agreement to pass laws in the areas already given to it, making its law-making authority closer to that of the Scottish Parliament.