The first section opened was between Walthamstow Central and Highbury & Islington. There was no opening ceremony for this. The normal timetable started on 1 September 1968. The first train left Walthamstow Central for Highbury & Islington at about 7:32 am. Later that year, the section between Highbury & Islington and Warren Street was opened. Again there was no ceremony.