Detective Superintendent Helen Millichap of Newham Police described the attack on the 16 year-old as "really unusual". She hopes the attacker will quickly be identified.
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Two members of the public were injured along with two police officers who were in the unmarked vehicle.
Scotland Yard recorded 1,235 Islamophobic attacks in the last 12 months, compared with 811 in 2015.
Officers say the child, aged two, was targeted in the Lewisham Shopping Centre.