Coffee pot signals developed from the very early types of signals in use on the tube and indeed these were derived from the most simple hand held railway lamps. When exactly it was that coffee pots signals were first used on London’s underground is not known, although general consensus is that it was around 1910-1912 when these first came into use. Research has shown that coffee pots were possibly used as calling on or shunt signals to begin with, which does sort of fit in with their use as hand held station lamps and the rest of it. Those types of station lamps have been in used since about the late 1880s and that because it was a style that was easy to make and one which conformed to certain standards – especially the use of glass which afforded subtle magnification in illumination – and indeed some used Fresnel type lens.
Coffee pots signals have been examined at length in previous posts dating back to 2016 especially in light of the fact a number were still in use on the sub surface lines prior to the implementation of CBTC. The last examples of these used in the central area was March 2021 when SMA3 went live and those coffee pot signals in question were at Baker Street, Great Portland Street, Euston Square, Barbican and Liverpool Street stations. One other example survived longer and this was that at Putney Bridge station which lasted until the section south to East Putney went to CBTC.
Header and initial paragraph of the first post on coffee pot signals – written seven years ago in 2016!
The history of London Underground’s coffee pot signals hasn’t been written about since 2018 although their redundancy was mentioned in a number of posts on the implementation and expansion of the Four Lines CBTC. Thus this post is a combination of a draft last updated in 2018 plus some new findings that enables the history to be brought up to date. In the above introduction from 2016 Liverpool Street (Central London Railway) was mentioned as being an early user of coffee pot signals and it has generally accepted that coffee pot signals began use around 1910-12. However its been found that Earl’s Court sported coffee pot signals earlier than that thus the District (and also the Piccadilly) line used these type of signals to an earlier date. PS – Most of this post was written as a draft in 2018 with some re-editing for 2023 to bring it up to date.
Earl’s Court early 1900s (LT Museum says c1905). This was from Greatest Capital’s tweet – the entire account has now been deleted. Some tweets I screencapped in dark mode as it looked nicer with the thread at the side. But what this picture does is shows there are four coffee pot signals combined with the semaphore signals then in use – hence the coffee pots were an early form of electric colour light signal – but as a platform repeater rather than a main starter.
In this screencap from another Greatest Capital tweet the semaphore signals can be easily seen. LT Museum dates it to c1906 – which is likely correct because the lifts to the Piccadilly Line can be seen. Railway Technic suggests it is 1904 which is rather unlikely in view of those lifts.
This image from LT Museum shows the coffee pots close up with the semaphores evident in the background. Although this is c1911 its enough to show these early electric colour light signals were used in conjunction with semaphore signals on London’s underground.
As the three different views of Earl’s Court station show, coffee pots were indeed in use from an early date although the exact date isn’t known. It could be anywhere between 1906 and 1911. However there is one aspect which dates it nearer to 1906. Its the fact steam locomotives are still in use as seen in the second image. The locomotive can just be seen through the bridge. Although the District Railway largely ceased use of steam in 1905 these were still used occasionally until at least 1907.
Having mentioned the Piccadilly Line (which was in those days known as the Great Northern, Piccadilly and Brompton Railway and opened in December 1906) it does turn out that the very first signals on this new railway were in fact coffee pot signals with elaborate mechanisms to show different colour aspects. This again shows this particular style of signal was most definitely in use from 1906 onward.
It was however a crude type of signal and the fact the earlier Waterloo & City Railway had gone for far superior type of electric colour light signal does demonstrate the Piccadilly railway had regressed in terms of signal design. Evidently it would have been a very expensive job equipping the entire line from Earl’s Court to Finsbury Park with those used on the Waterloo & City. The technology using an established coffee pot design was evidently much cheaper to produce en masse! The Piccadilly railway used classic semaphore signals at its Hammersmith and Baron’s Court stations, this being its only open air section of route at the time. Otherwise it was these particular style of electro-mechanical signals that were used on the remainder of the line.
Examples such as these clearly have what can be considered the forerunner of the coffee pot signals. The first example is this pair of signals at Holborn controlling the junction with the Aldwych branch.
The coffee pot lineage is not very evident here. What is important is the vent top, which clearly shows how these particular signals (and many other similar) were an evolution from oil lamps and this was carried over into the coffee pot signals. The moving lenses in front of the signals themselves is also important. Its a twin lens with a single lamp behind and the lens moves up or down to show either red or green. The single lamp housing behind was built in the style of what was essentially a single lens coffee pot signal. The actual porthole through which the light shone was about half the diameter of the glass itself. Around this was a circular reflector which would be painted white. This increased the illumination and spread the light to the whole surface of the glass.
Like the first example, this is on the Great Northern Piccadilly and Brompton Railway at Finsbury Park – this one is sited just before the crossover south of the station.
I have cropped the picture to show the ‘coffee pot’ housing behind the moving section of the signal. Although it is not a brilliant picture at least it does show this is a single lens coffee pot signal! The reflector is black however its inner edge will without a doubt be painted white as was the rule with these types. The output was a white light however the moveable lenses section gives either a red or a green aspect.
Whilst these early 1906 examples of signals on the Piccadilly Line must have served their purpose, the issue with these signals was of course the moving parts for it was a very cumbersome design with a electro-magnetic motor, rocker assembly and weighted balance lever.
The simple resolution to having such a cumbersome apparatus was to dispense with the entire mechanism save for the bit that housed the one lamp. That housing would be made somewhat larger in order to accept two lamps and of course two reflectors with better glass to boot. Whether it was the Piccadilly or the District railways that first devised the twin lens coffee pot signal is anybody’s guess.
It does seem that the District was the first to properly use the standard twin lens coffee pot signal. Other lines’ stations soon began to utilise coffee pots as repeater signals for train guards as in the case of Earl’s Court, and these worked in conjunction with the semaphores then in use. Their use soon spread to the deep level tube lines and many stations saw coffee pots in use both as repeaters and as main starting signals and at tone time could be found right across the Bakerloo, Central, Northern and Piccadilly lines – with a good number in use on the Northern until the early 2000s.
This Gettys/Topical Press Agency image from Liverpool Street Central London Railway in 1912 shows an early example of a coffee pot in use on the tube. Amazingly its the same exact style that was largely in use until 2021!!
By 1912 the design of coffee pot had reached its zenith as far as London’s underground railways are concerned. In terms of the signal housing itself and the bracket that suspended the signal from the ceiling these remained as they were until just two years ago when the Four Lines’ CBTC was largely implemented in the central area.
As this Flickr picture shows coffee pot signals had various brackets which could make the whole set up look quite elaborate if so desired. Yet the technique remained simple. This is Clapham North.
One thing is the signals were possibly built by a number of manufacturers but in due course Westinghouse were on the job too. Westinghouse built a version for use on the main line railways yet very few pictures showing these particular types of signals at work have been found. This Flicker page does show such examples in use during the sixties at Leicester Midland station. What is surprising with these Leicester pictures is the signals’ lens housing had become somewhat more modern yet the concept still remained the same – that is the main body of the signal was a coffee pot with a classic hood over the top.
Curiously the Metropolitan Railway too used coffee pot signals on its main line out into the sticks. It seems the stretch between Great Missenden and Wendover had a number of coffee pots though these may have been improvised versions which were placed upon the old signal posts in place of semaphores. There appears to be no pictures so the exact nature of these is not known. This re-use of older type signals on London’s underground network wasn’t completely unusual for it is known some of the old City & South London railway signals found new life on the Chesham branch!