63 years after Algeria proclaimed independence from France, its former colonial power, the two countries' relationships have gone through highs and lows. Today, they are at a historic low, so much so that the Franco-Algerian migratory agreement signed in 1968, under which Algerian nationals would have special rights in France, is now under threat.   Algerians made up 16% of foreign-born people in France last year, making them the number one foreign population.   Antonia Kerrigan takes us through the content of this deal.