It is a pioneering work — indeed it is thought to be the prototype for Telford's Pontcysyllte aqueduct. At around the same time, Benjamin Outram was planning his cast iron aqueduct for the Derby Canal.

Telford's chance to try his design came about because the original engineer, Josiah Clowes, died unexpectedly in 1795. Clowes had designed a conventional masonry one, the partially constructed arches of which were carried away by flood waters.

The trough is 9ft wide, 3ft deep and 187ft long. The towpath is carried on either side, level with the bottom of the trough. It is supported on slender 3-legged piers set in masonry.