Former Metropolitan Police Officer Graham Whettone has told Daybreak that security protocols surrounding Margaret Thatcher's funeral will most likely be reviewed in light of what happened at the Boston Marathon.
He said: "If they need to advance [the plans] then they will do, there's different tactical options the police can employ at various events, they will just review those now, if they need to advancer them then they will do."
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The families of all four of the victims, all of whom were men, have been informed, police said.
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