Sussex remained in France, and was used by the Marine Nationale at Le Havre. She was repaired post-war, and in 1920 was sold to D Demetriades, Piraeus, being renamed Aghia Sophia. She was scrapped in 1921 following damage sustained in a fire.
SS Sussex was built by William Denny & Bros Ltd for the LBSCR. She was launched on 30 April 1896. She served on the Newhaven – Dieppe route. In 1913, Sussex was replaced by the Paris and was laid up. She was sold in 1914 to the Compagnie des Chemins de Fer de l’État Français, remaining under the management of the LBSCR.
During the First World War, shipping from Newhaven was diverted to operate from Folkestone in order to free Newhaven for supplying British troops on the Western Front.
On 24 March 1916, Sussex was on a voyage from Folkestone to Dieppe when she was torpedoed by SM UB-29. The ship was severely damaged, with the entire bow forward of the bridge blown off. Some of the lifeboats were launched, but at least two of them capsized and some passengers were drowned. Of the 53 crew and 325 passengers, at least 50 were killed, although a figure of between 80 and 100 is also suggested. Sussex remained afloat and was eventually towed stern-first into Boulogne harbour.
The dead included the celebrated Spanish composer Enrique Granados and his wife Amparo. Several Americans were injured, but none were killed. However, although no US citizens were killed, the incident enraged public opinion in the United States of America, and caused a heated diplomatic exchange between the US and German governments. In May 1916, Germany issued a declaration, the so-called Sussex pledge, which effectively represented the suspension of the “intensified” U-boat campaign.
Between 1 and 3 January 1917, HMS Duchess of Montrose, HMS Myrmidon, HMS Nepaulin, HMS Redcar, HMT Security assisted in the salvage of Sussex, each ship receiving a portion of the salvage money.