The High Court has reserved judgment on the extradition of radical cleric Abu Hamza until a later date.
His QC says that an MRI (magnetic resonance imaging) brain scan could establish that he is unfit to plead and should not be extradited to the United States to face trial on terrorism charges.
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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.