At Combe Hay, the steep valley required the canal to climb a significant height—134 feet (41 m)[1]—over a distance of 1.6 miles (2.6 km).

[4] Adverts were printed in Bath periodicals in January 1796 to recruit stonemasons for building the locks.

[6] These showed that it could be traversed in 7 minutes; on 9 June 1798, a reporter for the Bath Herald wrote that: It is a pleasure to reflect that the hydrostatical contrivance for conveying of boats from upper to lower levels and vice versa, is completed, and may now be esteemed one of the greatest discoveries of the age; every scrupulous objection to the practability of its operation being removed.

[7]The same publication wrote the following year that the system was so simple that a boat could traverse the caisson in just 10 minutes under the operation of a 12-year-old boy.

[7] The report identified problems with the caisson's ability to remain watertight,[5] and hypothesized that the only solution would be to rebuild the chamber.

[6][9] In May 1801, having moved to Bath upon her father's retirement, Jane Austen wrote to her sister Cassandra about plans with her uncle to "take the long-planned walk to the Cassoon";[10][11] the short trip was a popular excursion at the time.

[12] The same year, Richard Warner wrote of the then-state of the caisson lock in his Excursions from Bath:[13] The deviation of a few hundred yards from the road to Combhay, leads us to the hydrostatical lock, called the caisson, the bason of which now alone remains [...] the machine was consigned to destruction, but not to oblivion, since it will ever remain a memorable proof of the superior mechanical abilities of its very ingenious inventorThe precise location of the caisson locks (or their intended location) is in doubt.

To achieve this, in June 1800 the company made the decision to build a temporary inclined plane to transfer cargo,[9] although this method for climbing the hill proved slow.

[6] The inclined plane was only ever intended to avoid further delays to the canal's construction,[16] and would only be in operation while the flight of locks was built.

[16] To reduce the length (and gradient) of the inclined plane, three pound locks were built to the east of Combe Hay.

[27] General restoration work began on the lower lock flight (below the Bull's Nose) in 2000.

This work was expanded to cover the upper flight in 2011, as landowner permission needed to be sought.