Complex sentence: This allowed her to get a job first in the London County Council (until 1917) and later in the Labour Research Department (1917-1920), which towerds the end of the First World War, became the center of the young leftist intellectuals.
Split into simpler sentences: This allowed her to get a job first in the London County Council (until 1917) and later in the Labour Research Department (1917-1920). This department towards the end of the First World War became the center of the young leftist intellectuals.