The prosecution is opening its case against Dale Cregan and nine others at Preston Crown Court. He denies murdering two police officers and two other men.
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Witnesses reported hearing a "huge bang" at the venue during the concert on Monday evening.
ITV News travels to Britain's eastern-most city to gauge how the electorate will be casting its votes.
Carefully choreographed campaigns can become unstuck because voters have the power to peel back a politician's veneer.