From the Evening Standard.
Police were also warned to "react professionally to the events in front of them" in briefing sessions in advance of the protests.
In addition supervisors were told to ensure officers displayed ID numbers, according to the report being presented to the Metropolitan Police Authority today."
"Sir Paul has already angrily criticised officers who fail to wear ID numbers and warned they face the sack if they did so deliberately. Video footage of the G20 protests has shown a handful of officers did not display them."
Well, that's all right then, isn't it? Obviously it was entirely accidental.