Legality of Cannabis by U.S. Jurisdiction Weir on the River Lea in Hertfordshire, England 51°47′13″N 0°05′12″W / 51.787037°N 0.086657°W / 51.787037; -0.086657 Horns Mill Weir in high flows Horns Mill Weir is a weir on the River Lea, next to Horns Mill, Hertford. Locks and weirs on the River Lea, EnglandCounties Bedfordshire Hertfordshire Essex Greater London Locks Hertford Lock Ware Lock Hardmead Lock Stanstead Lock Feildes Weir Lock Dobbs Weir Lock Carthagena Lock Aqueduct Lock Cheshunt Lock Waltham Common Lock Waltham Town Lock Rammey Marsh Lock Enfield Lock Ponder's End Lock Pickett's Lock Stonebridge Lock Tottenham Lock Pond Lane Flood Gates Old Ford Lock Bow Locks Weirs Horns Mill Weir Hertford Castle Weir Hartham Weir Ware Weir Feildes Weir Dobbs Weir Carthagena Weir Kings Weir Newmans Weir Middlesex Filter Beds Weir Hertford Union Canal(branch from Hackney Cut) Hertford Union Bottom Lock No. 3 Hertford Union Middle Lock No. 2 Hertford Union Top Lock No. 1 Regent's Canal Limehouse Cut(branch, at Bow Locks) Bromley Stop Lock Britannia Stop Lock Limehouse Basin Bow Back Rivers (branches of theOld River Lea) Three Mills Lock City Mill Lock Carpenter's Road Lock Marshgate Lane Lock (defunct) Three Mills Wall River Weir (These rivers form the waterways within the 2012 Olympic Park - they flow into Bow Creek)