Junior doctors, nurses and other health workers have marched from St Thomas' Hospital to Whitehall to protest at the removal of the NHS bursaries.
The government plans to scrap the bursary from 2017 and ask future nurses, midwives and other allied health professionals to take out student loans.
Many protesting on Saturday morning claimed that students would be taking out loans to work in hospitals. The present bursary pays the equivalent of about £3 an hour.
"What we need is to get together," said Green Party leader Natalie Bennett addressing the marchers in Belvedere Road.
"We will defend our NHS. We will defend the pay and conditions of workers in the NHS. We say bursary or bust."
A junior doctor was loudly cheered when she said that the first strike for forty years would go ahead the following week.
For the latest local news and events direct to your inbox every Monday, you need our weekly email newsletter SE1 Direct.
7,000+ locals read it every week. Can you afford to miss out?
Read the latest issue before signing up