SS Agamemnon was one of the first successful long-distance merchant steamships. She was built in 1865 to trade between Britain and China, and competed with tea clippers before and after the opening of the Suez Canal in 1869. She brought together three improvements in steamship design: higher boiler pressure, an efficient and compact compound steam engine, and a hull form with modest power requirements. Before Agamemnon, steamships were not a practical commercial option for trade between Britain and the Far East. The amount of coal that they needed to carry left little space for cargo. Agamemnon could steam at , consuming only 20 tons of coal a day. This was substantially less than other ships of the time – a saving of between 23 and 14 tons per day was achieved. This enabled her to steam to China with a coaling stop at Mauritius on the outward and return journey. Building and performance Agamemnon was the first of three sister ships, the others being Achilles (1866) and Ajax (1867). Scotts Shipbuilding and Engineering Company of Greenock, Renfrewshire built the three ships for Alfred and Phillip Holt's Ocean Steam Ship Company, later called the Blue Funnel Line. Each was and . Overall length was and beam . Agamemnon (and her sister ships) combined three key features. The first was a higher boiler pressure than was normally used on British merchant ships. Alfred Holt had experimented with a boiler pressure of 60 psi in the Cleator, a ship he used as a floating testbed. Holt overcame the Board of Trade's objections to boiler pressures above 25 psi in seagoing vessels. The second feature was her compound steam engine, designed by Alfred Holt. As well as being more efficient than others of the time, it was a relatively compact engine, so used less cargo space. The third was a hull that was strong in relation to its weight and cost and with modest power requirements – again developed by Alfred Holt. Agamemnons fuel efficiency enabled her to compete successfully with tea clippers between Britain and China. She could steam from London to Mauritius, a distance of 8,500 miles (roughly half the distance to China via the Cape of Good Hope) without coaling. Her normal journey time from Foochow to Liverpool was 58 days, whereas clippers could take anything from a record-breaking 88 days to 140 or more, and averaged 123 days in 1867–68.