 The young "socialist idealist and enthusiast" Bell found the rather mild and ameliorative program of the ILP insufficient and in 1902 he began to attend economics classes conducted by the Social Democratic Federation (SDF), headed by Henry Hyndman, which introduced Bell to the literature of Marxism.In February 1903, Bell left the ILP and enrolled as a member of the SDF.Some of the SDF classes which Bell attended were led by George Yates, an engineer by trade who impressed the young Bell with his skill as an orator and knowledge of economics, history, and politics.