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THE SIGNAL BOX

PHOTO GALLERY

British Railways (London Midland Region)

HARPENDEN JUNCTION

Opened: 1957

Closed: 1979

Location code: LM44/05


Harpenden Junction signal boxA new box was constructed at Harpenden Junction in 1957 in connection with the introduction of Diesel Multiple Unit trains on the suburban services between St. Pancras and Bedford.

Between Harpenden and Bedford, the Goods Lines were upgraded to passenger status as Slow Lines to cope with the increased service.

The box was a standard BR (LMR) 1954-design structure, comprising a timber operating floor on a brick base. The flat roof was not quite horizontal, but was tilted slightly downwards towards the rear.

Notice the engine number-taking lamp mounted on the front wall, a common feature at key locations in steam days as this was often the only way to properly identify freight trains.


Inside Harpenden Junction signal boxAs might be expected with a box built during this era, the interior was smart, clean and functional but nevertheless austere.

A 45-lever BR(LMR) frame was provided - this was a development from LMS practice which in turn had its origins with the Midland Railway. Frames with the mechanism above floor level like this were rare elsewhere.

This important location on the Midland Main Line controlled running junctions between the Slow and Fast Lines and also the junction for the former Hemel Hempstead branch, which in later years was a privately operated branch serving a works at Claydale. With their own locomotives, they placed their wagons near the outlet point during the daytime. These would be collected and replaced by a BR Luton to Brent trip service just after midnight. Shunting involved the use of both Fast Lines for standing wagons, so this could not be done by day.


Block instruments at Harpenden JunctionThe block instruments had their origins with the London & North Western Railway. They had been adopted as standard by the LMS, and continued to be used by BR(LMR) until the standard BR instruments had been designed.

The left-hand instruments shows "Down Line Clear" as a train has been accepted on the Down Slow. Notice the disused sealed glass release which at one time would have released the instrument in the case of failure of the distant signal.

Both instruments have Welwyn Control time releases - these are the round grey devices on the front of the shelf. The handle had to be rotated about 80 times before a second "Line Clear" indication could be given after a train had been accepted. The turning of the handle was supposed to give the signalman time to think whether he was doing something unsafe. These devices were only used if a train hadn't passed through the section - normally its passage would be identified by the occupation of track circuits.

Between the two instruments is a Midland Railway three-position closing switch. These had a luxury feature over more conventional devices in that mid-position allowed a signalman to spy on the indications showing between the two adjacent boxes when preparing to switch in. The switches were in fact rarely used at this location as the box was normally manned continuously.

The box had, in later years, a friendly squirrel that used to reach the windows via the roof of the relay room behind. He would rattle his claws on the window until you opened it, and would then demand a Chocolate Digestive biscuit. If you offered him any other kind of biscuit, he would throw it on the box floor in disgust.

Harpenden Junction box closed on 21st October 1979, in connection with the electrification and resignalling of the line. Thus the life of the box neatly matched the presence of diesel suburban services on the line.

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All photographs copyright © John Hinson unless otherwise stated