The River Lark crosses the border between Suffolk and Cambridgeshire in England. It is a tributary of the River Great Ouse, and was extended when that river was re-routed as part of drainage improvements. It is thought to have been used for navigation since Roman times, and improvements to its navigability were made in 1638 and in the early 18th century, whe…The River Lark crosses the border between Suffolk and Cambridgeshire in England. It is a tributary of the River Great Ouse, and was extended when that river was re-routed as part of drainage improvements. It is thought to have been used for navigation since Roman times, and improvements to its navigability were made in 1638 and in the early 18th century, when locks and staunches were built. Special powers to improve the river from Mildenhall to Bury St Edmunds were granted by statute. The upper terminus was on the northern edge of Bury St Edmunds, but a new dock was opened near the railway station after the Eastern Union Railway opened its line in 1846.