The 6S units were intended to be introduced into service in June 1957. On 5April a fire at Cannon Street signal box disabled all signalling equipment there. As a result, locomotive-hauled trains were banned from the station. A temporary signal box was commissioned on 5May and the 6S units were introduced on peak services the next day. Two units coupled together formed the 06:58 and 07:26 Hastings–Cannon Street services in the morning, and the 17:18 and 18:03 Cannon Street–Hastings services in the evening. From 17June the 6S and 6L units were working services throughout the day. The 6B units entered service between May and August 1958.