Deputy Mayor for Policing Stephen Greenhalgh, who is also being quizzed by the committee, said that they were "not complacent" about the Sapphire rape investigations unit and were "not saying everything has been learnt".
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Scotland Yard said the male youths will appear in custody at Westminster Magistrates' Court on Saturday.
The family of Oliver Dearlove urged people to "think again" before using their fists, as the man who killed him began a six-year jail term.
London Fire Brigade took Southwark Council to court on four charges in relation to safety breaches at Lakanal House in Camberwell.