Hundreds of protesters, many of them masked, took part in the protest which began in Trafalgar Square and moved to parliament.
Demonstrators chanted "Whose streets? Our streets" and "One solution, revolution" as they marched accompanied by police.
In a breakdown of an earlier tally of the arrests, when 33 people had been detained, police said 14 people were arrested for drugs offences and 11 for obstruction. One person was arrested for criminal damage.
Similar marches linked to Anonymous were due to take place in other cities around the world on Saturday.