The Leveson inquiry will hear today from Detective Chief Inspector Brendan Gilmour. DCI Gilmour worked on the Metropolitan Police's Operation Glade, which looks into police corruption.
The temporary Assistant Chief Constable of Devon and Cornwall police, Russell Middleton will also give evidence. He was involved in Operation Reproof about an officer allegedly supplying private investigators with information from the police national computer.
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Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.
As temperatures climb through the day, the warmest spots are likely to be across western parts of Northern Ireland and western Scotland.