Welcome to our feature on the proposed EU Constitution. There are some points to bear in mind.

First - the terms 'Constitution' and 'Constitutional Treaty' get used interchangeably. Any changes to the current Treaty establishing the EU (The Treaty of Nice) are decided by governments ('intergovernmentally') who will sign a new Treaty.

Second - the European Union has already got a Constitution of sorts - although like the British Constitution - it is not all in a single document. The term acquis communautaire is used to summarise the current body of Treaties, European Community legislation and European Court judgements passed over the years. Most significantly this contains a ratchet that any powers transferred by member states stay at a European level.

Third - the official EU documents approved by its Convention are subject to agreement between EU member states' governments and are therefore subject to change. There are 25 members and any could insist on changes - although history also shows that compromises take place.

Fourth - some countries, notably Denmark and the Republic of Ireland require referendums for what will be constitutional changes for them. Treaty ratification has to be unanimous, otherwise the new [Constitutional] Treaty does not come into force.