NHER 58825 (Building record) - Post medieval signal box

April 2013. Listed. Grade II.
List Description (S1): Signal box built for the Great Eastern Railway in 1883.
MATERIALS: reddish-brown brick laid on Flemish bond and slate roof covering.
PLAN: it stands immediately to the west of the main station building on the north side of the line, and is rectangular on plan with a rear extension.
EXTERIOR: the signal box has a pitched roof with boarded gable ends and overhanging eaves. The bargeboards and south (front) fascia bear a decorative scalloped moulding. The ground-floor locking room is divided by brick pilasters into three panels with decorative cogging, each panel pierced by the original six-light window with glazing bars and segmental arched brick heads. It is accessed via a timber plank door on the west side. The front and much of the side elevations are continuously glazed with horizontal sliding windows: the front has six twelve-pane windows, the east side has two twelve-light windows followed by one nine-light window, and the west side has two twelve-light windows. A balcony for cleaning the windows runs around three sides of the building. The upper operating floor is accessed via an external flight of metal steps, dating from the third quarter of the C20, through a timber door with glazed upper panels, which is not the original. There is a lean-to extension on the north side, dating to at least 1905, which has, on the west side a timber plank door, and a small flat-roofed extension, added in the second half of the C20.
INTERIOR: the signal box retains its original 1883 McKenzie & Holland lever frame to their pattern of c1873. A false ceiling has been inserted and secondary glazing fitted.
HISTORY: From the 1840s, huts or cabins were provided for men operating railway signals. These were often located on raised platforms containing levers to operate the signals, and in the early 1860s the fully glazed signal box, initially raised high on stilts to give a good view down the line, emerged. The interlocking of signals and points, perhaps the most important single advance in rail safety, patented by John Saxby in 1856, was the final step in the evolution of railway signalling into a form recognisable today. Signal boxes were built to a great variety of different designs and sizes to meet traffic needs by signalling contractors and the railway companies themselves.
Signal box numbers peaked at around 12,000-13,000 for Great Britain just prior to the First World War, and successive economies in working led to large reductions in their numbers from the 1920s onwards. British Railways inherited around 10,000 in 1948 and numbers dwindled rapidly to about 4000 by 1970. In 2012, about 750 remained in use; it was anticipated that most would be rendered redundant over the next decade.
Thetford Station was opened in 1845 as part of the Norwich & Brandon Railway which was later incorporated into the Great Eastern Railway. The signal box was built in 1883 when block signalling was installed on the Ely to Norwich line. Like most of the other boxes on the line, it was built to the GER Type 4 design which is distinguished by being of brick construction, rather than the timber used on most GER boxes from the 1880s. The box has a single-storey extension on the north (rear) side which is shown on the second edition Ordnance Survey map of 1905. A further small extension has since been built onto the west side of this.
Compiled by H. Hamilton (HES), 24 May 2013.