Socialist Party youth activists gathered in St John's Churchyard on Thursday morning for a rally and march to Excel where the G20 summit is being held.
The 'Youth Fight for Jobs' campaign is calling for an £8 living wage, for better pay for apprentices and an end to university tuition fees.
A minute's silence was kept in memory of the man who died during Wednesday's G20 protests near the Bank of England.
At London Bridge Walk staff at Richer Sounds rushed to close the shop's shutters as the noisy demo approached.
There were chants of "Gordon! Gordon! Gordon! Out! Out! Out!" as the march approached Southwark Bridge.
At Southwark Bridge the marchers received a round of applause from a small gaggle of staff outside the offices of the Health & Safety Executive.
Ambulances from as far afield as the East Midlands and the South Coast were on standby in Tooley Street as the rally got under way.