Detective Superintendent Stephen Ratcliffe said this was "a gang of experienced criminals who had been the subject of an investigation by the special projects team at the Metropolitan Police for a couple of months before this robbery."
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Two men have been taken to hospital after a "suspected acid attack" in east London.
Mr Gard and Miss Yates want to spend the final hours with their son at home in Bedfont, west London.
A ninth penguin was injured.