Arnis Zalkalns, left, the Latvian who murdered his wife before moving to the UK where he killed 14-year-old Alice Gross, right
Violent: Dawid Tychon, left, was the ringleader of a Polish gang who attacked Paul Kohler, 57, right, at his home in south-west London. Professor Kohler suffered appalling injuries when he was beaten in front of his family
Violent: Dawid Tychon, left, was the ringleader of a Polish gang who attacked Paul Kohler, 57, right, at his home in south-west London. Professor Kohler suffered appalling injuries when he was beaten in front of his family
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