The European Union started with just 6 member countries. Over the years 6 more - including the United Kingdom - joined the community. But it was in 2004 when the single largest expansion saw 10 more countries join in one go. And with membership came freedom of movement. Mark Mardell looks at what impact this had on Britain's relationship with the EU and whether enough consideration was given to the number of people who would come to live and work in the UK? Email: worldatone@bbc.co.uk. Twitter: @BBCWorldatOne