It was envisaged that the line would stretch from the
River Medway to the
Thames but a shortage of money meant only five of the original large works plus two small experimental earthen redoubts were built. Work, using convict labour, started 30 years later in 1890, but by that time the enemy it was supposed to repulse,
France, was an ally, the new enemy was Imperial
Germany. Because of budget restraints and changing fashions in fortifications, no fixed armament was mounted; instead earthen ramps were built to enable field artillery to fire from the fort's parapet. The fort was a radical departure from traditional design, of earth construction, with a deep dry moat designed to blend in with the line of the land. There were magazines and living quarters under the earthen walls. A new large prison was built on the hill above the nearby village of
Borstal to house the workforce. It later became a prison for young offenders and gave its name to the Borstal Institution system of correction.
Railway Four of the forts (
Luton,
Horsted, Bridgewoods and
Borstal) were linked by an gauge railway to move building materials between the sites, called the Eastern Defences Railway (EDR), built by the
Royal Engineers. Building materials were brought by barge up the
River Medway to a quay at Borstal, then hauled up the steep scarp slope of the
North Downs to the fort via a branch of the EDR. This was done using a special type of locomotive called a Handyside locomotive that could be clamped to the tracks while it hauled wagons up behind it in stages using a winch mounted on the front of the loco. The prisoners were transported along the EDR in lockable carriages, accompanied by armed warders. The railway remained in use until about 1905. Some of the original railway lines can be seen in the cow-shed floor of the prison farm, which in a previous incarnation was the railway workshop. The line of a section of the track between Fort Bridgewood and
Fort Horsted can be seen from the air (for example on
Google Earth), as it curves away in a south westerly direction from the junction of City Way and Marconi Way. == World wars ==