The history of the world is the history of people moving. For as long as we have been aware of pastures new, we have sought them - just as we have always fled fire, famine and flood. But this old and natural impulse has also provoked much tension. Why?
In this month's Penny Lecture, Robert Winder considers the place of migration in today's Britain, and whether the fear of it isn't more unsettling than the thing itself.