Hundreds of activists were expected to join the first international debate hosted by the London branch of new Spanish radical left party Podemos this Saturday.
Podemos MEP Tania Gonzalez and campaign director Iñigo Errejon are coming to speak at the meeting.
It is entitled “Rethinking ourselves: Podemos as part of a new construction of democracy in Europe”.
Other platform speakers include Guardian columnist and Labour Party activist Owen Jones, and film director and Left Unity founder Ken Loach.
The Socialist Workers Party will be among those taking part in the subsequent debate.