In the late 1970s the United Kingdom Ministry of Defence (MoD) proposed a diesel-electric submarine design to replace the "Oberon" class. The new submarine class was intended to provide a more cost-effective alternative for training and in coastal defence. The announcement for the new design took place in September 1979. Five designs were put forward, with the MoD selecting the 1,960-ton design. However, the need for export potential upped the displacement limit to 2,400 tons to allow for flexibility in construction if the need for alternative machinery and systems arose.