The increase in ships using the port led to congestion in the river. During the 1750s, nearly 1800 vessels were allowed to moor at the same time in the Upper Pool in a space intended for not many more than 500. Goods often stayed in lighters for weeks before they could be dealt with. They were exposed to the weather and well-organised gangs of thieves.
The West India Docks relieved congestion on the River Thames. Ships could discharge cargoes in four days instead of four weeks. The docks were surrounded by high walls which kept out the thieves.