Holme Sluices, which was built in the 1950s and opened by the late Prince Philip, spans the full width of the River Trent and is used by the Environment Agency (EA) to protect Nottingham from flooding and control river levels upstream. The sheer size of the barrier means it has for a long time been the largest obstacle to the natural migration of fish in the Midlands, which the new pass will now correct by using narrow slots and ascending chambers to allow salmon, trout, lamprey, eels, and other fish to swim past it.