At the Port of Dover in Kent, officials said this morning that cross-Channel ferry operations were operating "as far as possible".
Passengers are being advised to allow extra time for journeys ahead of possible road blockages on the A2 and A20.
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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.
Boris Johnson and Amber Rudd have both criticised social media giants for failing to detect and remove extremist material online.