In the three years since the European Union welcomed 10 new members, record numbers have moved from east to west. The scale of migration has cheered those eager to promote mobility within the EU and distressed those who fear the economic and social effects of un-controlled immigration. Yet both cheerleaders and detractors of Europe's newfound mobility are getting worked up by a temporary phenomenon.

There is no denying that the scale of movement, especially to the UK and Ireland, has been staggering. More than half a million new member nationals have registered to work in the UK since 2004, not including the self-employed and those who do not need to register. Poles, who account for more than half of this inflow, were the single largest immigrant nationality arriving in the UK in 2005. In Ireland, some 330,000 new member nationals obtained personal public service numbers - required to work or claim benefits - between May 2004 and February 2007. More Poles than Irish applied for these numbers in 2006. New member nationals have also made their presence felt in other parts of the EU - the infamous Polish plumber, for example - as many existing member states start to ease restrictions on movement of workers from new member states.