[3] James Brindley was appointed as the chief engineer, and having raised the capital in just four months, the proprietors instructed him to start work on 11 July 1771.

[7] Apart from a short section in the middle, the tunnel was lined with bricks, and so the company established a brickworks at Harthill, and advertised for brickmakers.

This should have been easy to do, as the area around Norwood Hill had plentiful coal deposits, but a clause in the Act of Parliament stated that all minerals found during the construction of the canal remained the property of the person from whom the land had been bought, and so the canal company had to negotiate with the Duke of Leeds to buy supplies of coal, in some cases from their own land.

[6] An intriguing aspect of the project occurred in May 1774, when the minute book records that five shillings (£0.25 (equivalent to £40 in 2023)) was paid to a Mr Samuel Watt on 22 May, for making a model of a machine to draw boats through the tunnel and demonstrating it to the Committee.

There have been suggestions that it involved a moving chain or rope, powered by a steam engine, but nothing further was heard of the idea, as no action was taken.

Sources dating from the construction, including the report in the Derby Mercury, quoted the length as 2,550 yards (1.449 mi; 2,332 m).

[17] Skempton, in his entry for John Varley, quotes the length as 2,884 yards (1.639 mi; 2,637 m), acknowledging that there is wide divergence across many publications.

The removal of coal from seams under the tunnel caused major subsidence problems - segments began to sink.

The raising of practically the whole length of the tunnel roof was done by prolonging the side walls and rebuilding the semi-circular arch.

After days of heavy rain a 12–14-yard (11–13 m) section of the tunnel collapsed on 18 October 1907, leaving a large hole in a field near the road to Harthill.