US Secretary of State John Kerry has said that US raids in Africa are a signal that the US "won't forget attacks and won't relent in fighting terrorism."
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Wintry scenes across the UK this late in April have not been seen since the mid-1980s.
The Labour leader will also announce an inquiry into anti-semitism and other forms of racism to be chaired by Shami Chakrabarti.
A switch in the wind direction will mean the unseasonably bitterly cold air of the last few days finally gives way.