A 50-year-old man was arrested in south east London on suspicion of conspiracy to commit murder, while three men in their 20s were bailed on the same charge.
Two suspects arrested at the scene of the crime, Michael Adebolajo and Michael Adebowale, remain in police custody.
Help for Heroes, the Armed forces charity, said last night it would not accept donations from English Defence League in order to maintain its stance as a non-political organisation. “ We would like to make it clear that we will not accept donations from organisations who attempt to use Help for Heroes to promote their own political agenda,” it said in a statement.
More than a thousand EDL supporters marched through central London yesterday, clashing with police and anti-fascist activists, forcing Whitehall to close.
In separate developments, two people were arrested in the Lincolnshire port town of Grimsby after petrol bombs were thrown at the local mosque, while central London war memorials were daubed with graffiti.
Meanwhile, Labour politician Jack Straw warned that proposals to ban radical preachers from television broadcasts and the internet could backfire and act as a “recruiting agent”. Home secretary Theresa May has also raised the prospect that the Tories could seek to reintroduce the so-called snooper’s charter legislation with Labour support, making it easier for the security services to monitor communications.