Seeking to avoid steep gradients along the line, it became apparent that a tunnel would be required near to Clay Cross.

[2][7] Construction began on 2 February 1837 when the first sod was turned for the sinking of the ventilation shaft in the centre of the tunnel.

[2] During August 1839, it was reported that excavation of the tunnel had been completed, and the final brick was expected to be laid within a few days.

The northern portal features a Moorish-inspired aethetic and is presently a Grade II listed structure.

[10] The south portal, which is also Grade II listed, comprises an arch is formed of two ashlar bands of roll moulding profile.

[2] Clay Cross railway station was at the northern end, where the line was met by that from the Erewash Valley.

The tunnel saw one of the first uses of the absolute block signalling system, maybe after a narrow escape on the south-bound inaugural journey.

This was detached at the entrance to the tunnel, but halfway through the train came to a halt, and someone had to walk back for the pilot, to the consternation of the passengers.