Unit 3: The changing UK system by Dr Alys Thomas Former Lecturer in Government at the School of Humanities and Social Sciences at the University of Glamorgan writes for BBC Parliament

Devolution has transferred power from Westminster to Edinburgh

The UK has been described as a unitary state because sovereign authority resides in Parliament at Westminster.

In reality, political arrangements in the UK have always reflected its 'multi-national' character.

Scotland has always had distinct legal and education systems. There has been separate legislation for the Welsh language in Wales and for security issues in Northern Ireland and before devolution all three had territorial government departments and a Secretary of State with a seat in Cabinet.

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However, devolution has transferred power from central government in London to bodies in Scotland, Wales and Northern Ireland.

UK devolution is characterised by asymmetry. Unlike a federal system, where states or provinces share sovereignty with the centre and have comparable powers with each other, the devolved arrangements in the UK differ sharply between territories.

UK devolution

Scotland - has a Parliament with primary law-making powers. It also has the power to vary the rate of income tax. The assumption in the Scotland Act is that all domestic policy functions have been devolved: the Act states what is reserved to Westminster, notably foreign policy, defence policy and social security.

Wales - has executive devolution. The National Assembly for Wales inherited the powers formerly held by the Secretary of State for Wales and the Welsh Office. It can pass secondary legislation (orders, regulations) but has no primary legislative powers or tax-varying powers. The Welsh Assembly Government still has to rely on England and Wales Bills to enact some of its policies.

The Northern Ireland Assembly was set up as an upshot of the ongoing peace process as part of the Good Friday Agreement. It has some primary legislative powers but no tax-raising powers. It has a power-sharing executive which requires parties elected by both sides of the religious/political divide to work together.

Critics of devolution argue that it made concessions to nationalist sensibilities which present a threat to the unity of the UK. Supporters argue that it was essential to accommodate those sensibilities in order to prevent the UK breaking up.

The part of the UK which remains undevolved is, of course, England which comprises by far the largest part both territorially and in terms of population.

However, the Labour Government has created Regional Development Agencies and appointed Assemblies to scrutinise their work. It has also come forward with proposals for elected Assemblies for the English regions.

These will be subject to demand and referendum so in the short term there is the prospect of some regions, such as the North East, having devolution and others being governed centrally. London already has a directly elected executive Mayor and a 25-member Assembly.

A key question for the future is the extent to which these asymmetrical arrangements are sustainable.

The current assumption seems to be that central government and Parliament will remain unaffected by handing power to devolved bodies.

However, there are already issues about the role of Scottish MPs in Parliament and the pursuit of different policy agendas around the UK.