Immigration lawyer Andrew Tingley says that new rules requiring foreign nationals from outside the EU to have a biometric residents permit had left the IT system unable to cope.
It was close to collapse a few weeks ago. It has now collapsed. It's an absolute mess
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Net migration to Britain was down 49,000 in the year to September 2016, the lowest level in more than two years.
Special forces say they have attacked a sprawling site adjacent to the city's airport in a bid to liberate the area from IS.
Flights and trains were cancelled or delayed and drivers were warned to steer clear of some main roads as winds of nearly 90mph hit.