A senior Met police detective is due to be sentenced today, after being convicted of trying to sell information to the News of the World about the phone-hacking inquiry.
April Casburn, who was found guilty of misconduct in public office in January, was told by the judge that she could face a custodial sentence.
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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.