The Labour leader Ed Miliband has launched a scathing attack on the Coalition Government in his address to an anti-austerity rally in Hyde Park, London.
He said: "The culture of two nations runs right across this government. They cut taxes for millionaires and raise them for ordinary people".
He made a joke at the expense of the Chancellor George Osborne who "tries to travel first class on a standard class ticket" and described the Prime Minister as "weak and clueless".
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Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
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.