It is one of the few natural harbours on the north coast of south-west England and during the prehistoric and early medieval periods was important for trade and the movement of people and ideas.

Due to the estuary being one of the few natural harbours on the north coast of south-west England, it was important for trade and the movement of people and ideas.

Research on the inscription suggests it dates to the 5th-century AD, has European inspiration and the name is possibly Irish in origin.

Harvey's built South Quay in 1819 which increased silting in shipping channels; a problem initially resolved by impounding Copperhouse Pool.

The complex system maintained the port facilities which allowed the two competing foundries to increase their national and international roles.

Its western terminal was at Penpol (under the viaduct of the current railway), followed part of the northern shore of Copperhouse Pool and then via an inclined plane at Angarrack, on to Redruth.