What is an ‘ever-closer union’?

The preamble to the Treaty of Rome (1957), the international agreement that was the beginning of the EU, says that the signatories are “determined to lay the foundations of an ever-closer union among the peoples of Europe”. As it transpires, this has turned out to be a highly controversial sentence. David Cameron’s successful EU negotiations expressly sought to exclude the UK from this. Millicent Ragnhild Scott, who took part in the expert proceedings on the matter, in the LSE Commission on the Future of Britain in Europe, explains why.