A dog which attacked five police officers in Stratford is believed to have been responsible for another attack on a passer-by last year.
The officers were set upon in Albert Square yesterday morning.
One man has been arrested.
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Officers were given the touching letter at Brixton Station while they were on a reassurance patrol after yesterday's attack
The 52-year-old had previous convictions for violence but was not on the anti-terror watchlist.
In a statement Charlton Athletic said: Keith was a true hero who will be greatly missed by all the Charlton family and everyone at the club.