Scotland Yard said three arrests had been made before 7pm in relation to the anti-austerity demonstration which took place to coincide with the Queen's Speech and the State Opening of Parliament.
A 17-year-old youth was arrested on suspicion of assault.
A man, whose age has not been given, was arrested on suspicion of violent disorder and possession of an offensive weapon.
Police also arrested a 45-year-old man who was wanted on suspicion of violent disorder in relation to an incident in Whitehall on May 9th.
The party said the flower was worn in homage to poet Hugh MacDiarmid who wrote the ode 'The Little White Rose of Scotland'.
An EU referendum, more Scottish powers and tax freezes - but Cameron stopped short of scrapping the Human Rights Act, for now.
More powers for Wales, a ban on income tax rises and more free childcare are at the heart of the Conservative's Queen's Speech.