Eton College and the price of going underground
The London and Birmingham Railway, the first main line built into London, was begun at Chalk Farm on 1 June 1834. Robert Stephenson's route ran out of Euston, climbed through Camden Town and then had to get past the rising ground on the western side of what is now Primrose Hill. Nearly three miles of cutting were dug, and beneath the hill the line was carried in a tunnel of about 1,164 yards — a little over a kilometre.
The tunnel was not strictly an engineering necessity; the topography did not demand it. The land belonged to Eton College, owner of the Chalcots estate, which had obtained an Act of Parliament in 1826 allowing it to grant ninety-nine-year building leases. An open cutting would have destroyed the value of ground the college intended to let as building plots. Negotiations opened in 1831 and Eton set the terms: the railway would go underground, the tunnel would be built strongly enough that houses could stand on top of it, and the eastern portal — the end that the college's future tenants would look at — would be architecture rather than engineering.
Blue clay, a bankrupt contractor and a 27-inch lining
The ground turned out to be the hardest part of the whole line. The tunnel was driven through London clay, which was impermeable but so tough that men worked it with crosscut saws and hatchets rather than picks. Worse, once exposed to the air the moist clay swelled, pressing on the new brickwork. The answer was brute mass: a lining 27 inches thick, hard paver bricks in place of hollow London stocks, and Roman cement instead of lime mortar.
The contractors, Jackson and Sheddon, went bankrupt late in 1834. Stephenson took the work over and finished it with labour he employed and supervised directly. The contract price for the first section out of Camden Town had been £120,000; the eventual cost was more than double, at some £280,000. The tunnel was completed in January 1837, the first railway tunnel in London. Public nervousness about travelling underground was such that in 1835 four physicians, among them Sir William Lawrence, inspected the works and certified that passing through posed no risk to health.
A £7,000 gateway, still listed
The ornamental eastern portal cost Eton's insistence roughly £7,000, a very large sum for what is essentially a doorway; the western portal was left plain. Both were designed by William Budden, an assistant engineer to Stephenson, in an Italianate manner that Historic England has compared to Brunel's work at Box. Crowds came out to watch the trains disappear into it, and contemporary prints show sightseers on the embankment by the eastern end.
The eastern portals were listed at Grade II* on 14 May 1974 and the western portals at Grade II on the same day. A second bore was added on the southern side in 1879 by the London and North Western Railway, designed by its chief engineer William Baker, to give four tracks between London and Watford; it copied the original portal design, though taller, because the ground above rises. A third pair of tunnels followed in 1912 for the Watford direct-current line, now used by London Overground services calling at South Hampstead. The Great Central Railway's viaduct of 1899 now obscures the western portals. Two ventilation shafts survive above, one in a hotel car park and one at 10 Wadham Gardens.
Ropes, chimneys and the Camden incline
Between the tunnel and Euston lay a second problem: the gradient down to the terminus was too steep for early locomotives, and residents objected to engine noise and smoke close to the houses. Stephenson's solution was a stationary winding engine, housed in vaulted chambers beneath the main line just north of the Regent's Canal bridge, with two steam engines of 60 horsepower driving an endless rope some 4,080 yards long that hauled trains up the bank. Trains ran down under gravity, controlled by a brakeman, with locomotives attached at the canal. The engine house's twin chimneys, 133 feet high, became local landmarks and something of a tourist attraction. The system was abandoned in April 1844 once locomotives could manage the climb unaided, and the chimneys came down. The vaults themselves survive.
Goods yards, stations, and the neighbourhood that did not happen
The passenger line to Boxmoor opened on 20 July 1837 and the full route to Birmingham on 17 September 1838. Freight stayed at Camden. The goods depot opened in 1839 on 25 acres north of the canal, later expanding to around 33, transferring goods to road carts or to the Regent's Canal for the docks until a direct rail link to the docks was achieved in 1851. The Roundhouse of 1847 — 160 feet across, with 24 tracks radiating from a central turntable — was built as an engine house for goods locomotives that had outgrown the earlier sheds.
The local station changed identity repeatedly. Hampstead Road opened in 1851, moved in 1855, was renamed Chalk Farm in 1862 and rebuilt in 1871. The main-line station closed in 1915, reopened on 10 July 1922 for the electrified service to Broad Street, was renamed Primrose Hill in 1950 and closed on 22 September 1992.
The railway's largest effect on Primrose Hill, though, was what it did not do. Eton's tunnel kept the surface intact for building, and the streets and terraces of the present conservation area went up on ground that would otherwise have been a cutting. Had the Great Western Railway not abandoned an early plan to share facilities with the London and Birmingham, much of that same ground would have been covered in sidings and sheds. Elsewhere the railway was less gentle: widening works between 1900 and 1906 required the demolition of one entire side of Park Village East.