Thus, Stephenson was forced to take a more difficult route to the east through a patch of high ground which required a sequence of cuttings, embankments, and a tunnel.

The majority of the tunnel's route is through chalk but test bores missed a patch of gravel and sand which workers struck while digging.

The railway historian Gordon Biddle considered the newer portals to have a "fortress-like appearance [...] in strong contrast to its delicately classical neighbour".

John Cooke Bourne illustrated the construction of the original tunnel in his series of lithographs, published to mark the opening of the London and Birmingham Railway.

Matt Thompson of the Ironbridge Gorge Museum Trust described the scene as showing the scale of the engineering work—"In places, the building of the railway reshaped the landscape and Bourne is at pains to demonstrate how big an undertaking this was".

[7] The south portal of the original tunnel was designated a Grade II listed building in 1983, a status which provides legal protection from unauthorised demolition or modification in recognition of historic and architectural value.