Angela Merkel has been speaking at a joint press conference with David Cameron in Westminster:
Merkel: What we are discussing here is "doable" but adds "I am a great champion of freedom of movement"
Merkel: Is immigration into social security possible? It's just as much a headache for us in Germany as it is in Britain
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The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.
As temperatures climb through the day, the warmest spots are likely to be across western parts of Northern Ireland and western Scotland.
The foreign secretary has criticised internet and social media giants for failing to detect and remove extremist material posted online.