Former Metropolitan Police Commissioners Lord Condon and Lord Stevens are due to give evidence to the Leveson Inquiry. Surrey Police Chief Constable Lynne Owens is also set to appear.
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Guillier conceded a "severe defeat" defeat to his supporters as the result came in.
The outage struck Hartfield-Jackson Atlanta International Airport at around 1pm local time, stopping all outgoing flights.
It will be a chilly day for many parts with the highest temperatures, about 10 Celsius (50F) in the far northwest.