Complex sentence: For a period in the 1960s he was a councillor in Newcastle-under-Lyme on the Labour Party ticket in which party IS was then resident, later writing an article in "International Socialism" on how the experience was politically dispiriting.
Split into simpler sentences: For a period in the 1960s he was a councillor in Newcastle-under-Lyme on the Labour Party ticket in which party IS was then resident. He later wrote an article in "International Socialism" on how the experience was politically dispiriting.