Primrose Hill Tunnel is a 1,164-yard (1,064 m) railway tunnel on the West Coast Main Line, approximately 2 miles (3.2 km) from Euston station. It is located in South Hampstead in the London Borough of Camden, just north of Primrose Hill park and consists of two bores: the slow line to the northern side, driven through the London clay by the engineer Robert Stephenson for the London and Birmingham Railway in 1838, and the fast line to its south, added by the London and North Western Railway in 1879. The original tunnel's Italianate portals were designed by William H Budden and later replicated for the fast line. The western portals have been listed at Grade II and the eastern at Grade II* since 1974.