Freedom of movement will be a key battleground in Britain's crucial EU debate. It gives EU citizens the right to live and work anywhere in the union and is praised by supporters as boosting prosperity. But critics say it has created unsustainable waves of mass migration and must be restricted. So where does this policy actually come from, and what does it mean in practice? Sonia Sodha discovers why it has become such a crucial issue, and what's at stake as Britain decides its European future.

Producer: Chris Bowlby

Editor: Hugh Levinson

(Photo credit: Getty Images)