LT Signalling Questions

...and some answers

In this section are set out a series of questions that have arisen about LT signalling matters to which further information would be welcome. At the bottom of this page is set out some answers that have been received as a result of previous queries

Current Queries

The register found on this website is the author's best attempt to set out in one place a huge amount of historical information relating to the various signal boxes (and other interlockings) on the London Underground. The number of sources used is very large and includes the National Archives (railway inspecting officer's records), technical publications (notably Railway News, Railway Gazette and the Railway Engineer), LT staff magazine and of course hundred of signalling notices issued by London Transport in its predecessors. Photographs in my own and other people's archives, and in magazines, are also very useful, as are old chronologies relating to the development of the LT network. Nevertheless there are gaps, and these are especially noticeable in the Victorian era. In due course the missing information will be extracted from the register and posted here so that anyone who might be able to help can see at a glance what is still needed.

For now, the focus on gap filling relates to the electro-pneumatic installations from just before the Second World War. In compiling the register, it has become apparent that not all of the information I require to produce a detailed inventory is actually given in the various signalling notices relating to signalling upgrades. Type of interlocking frame is only rarely stated, number of levers is not always stated and in some cases the exact location of the signal box or interlocking isn't very clear. Fortunately it is often possible to fill in the missing details from photographs or (a little less satisfactorily) from the memories of those who used to work in these signal boxes. Nevertheless, there are still some entries that are incomplete for want of information. The problem is more acute for the host of temporary frames which by their very nature are less likely to have been photographed or worked in by large numbers of staff.

If anyone has any information that might answer any of these points, I would be very grateful to hear. The questions are fairly specific, though, so I may well have quite a lot of peripheral information, especially that from the usual sources. I'm increasingly having to rely on photographs, or of personal recollections or access to official internal records not normally available or which might have been privately preserved.

Questions about power frame type.

1. Frame type used at 7-lever temporary box (cabin code MX) at Dollis Hill between 18 September 1938 and 2 April 1939 and do we know where it came from? Approximate location was on east side embankment at north end of station but is precise position known and what type of structure was it? (Must have been B frame)

2. Frame type used at 7-lever temporary box (cabin code MZ) at Preston Road between 6 November 1938 and 7 March 1948 and do we know where it came from? Approximate location was on east side of line, 400ft north end of station but I wonder if exact position known and what type of structure it was (probably where even today the cable run is set back about 6 feet). (Must have been B frame).

3. Frame type used at 23-lever temporary box (cabin code C) at Kings Cross between 16 March 1941 and 29 June 1958 and do we know where it came from?

4. Frame type and precise location of 59-lever temporary box (cabin code MG) at Wembley Park between June 1954 and 26 September 1954 and do we know where it came from? Notices state it was south of existing signal box. That puts it near where later staff canteen was situated; do we know exactly where the temporary cabin was (was it in the canteen which looks like it was built around that time anyway or was it a different structure)?

5. Answered and information incorporated, thank you

6. Frame type used at Euston (cabin code J) temporary box between 29 March 1958 and 15 November 1958? (Note this appears to have been a temporary frame in or adjacent to existing signal box).

7. Frame type and size used at temporary box (cabin code OE) at Moorgate (Metropolitan Line) between 21 June 1965 and 3 February 1966 and do we know where it came from (was located above part-built IMR on platform 6)? Note that although highest lever number was 24, the frame only controlled City Widened Lines part of station and no signals were renumbered so only 14 levers seem actually to have been used.

8. Substantially answered and information incorporated, thank you. Frame type used at 11-lever temporary box (cabin code D) at Holborn Piccadilly between 15 July 1979 and 1 March 1980 was a Style N. Do we know where it came from prior to use at Holborn?

10. Answered and information incorporated, thank you

11. Frame type and size of temporary box (cabin code AC) at Colindale between 3 April 1966 and 15 July 1967 and do we know where it came from (and then went)?

12. What was frame type and size of temporary box (cabin code JE) at Northwood Hills between 10 September 1961 and 16 June 1962 and do we know where it came from (and then went)?

12A. What was frame type of temporary 23-lever frame (cabin code E) at Camden Town between 24 July 1955 and 17 September 1955, temporarily controlling new IMRs and presumably using route levers. Also, do we know where it came from (and then went)? It was located in a cross passage between platforms and predated control desk.

Questions about when frame installed

13. Frame at Queens Park at time of closure (1990) was metal-clad and appears not to be same as that installed in 1915, though lever configuration same. Was it changed over at some time and, if so, when?

14. The Style B Frame at Archway at time of withdrawal (1992) was metal-clad (and seriously mucked about with) and appears not to be same as that installed in 1907. Was it changed over at some time and, if so, when?

14A. The frame at Baker Street when the signal box closed does not appear to be the same one that was introduced when the signal box opened in 1924 (39 lever style K number E19). The original frame was wooden cased and exactly same length as lever set. The frame at closure was metal cased and whilst still having 39 levers had an extension at right hand end for writing desk and telephone panel. Furthermore the frame appears to be closer to front wall than the original frame had been. This suggests whole thing had been replaced at some point (probably before 1960 as this number of levers was not required after track and signalling simplification around then, leaving frame with ten spare levers). It has been suggested frame was replaced in period 1947-52 and its replacement was probably a Style B frame, rather than a K. I'm looking for confirmation frame was replaced and an exact date and confirmation of type, and would like to know where replacement frame came from.

15. Date when the 19-lever B frame at Holborn (Piccadilly Line) was replaced by a smaller (11-lever) frame, also in a wooden case. This probably happened within a few years of 1930 (it is possible the existing frame was shortened, but judging by quality of the woodwork when this frame was finally taken out it is more likely it was simply swapped over for the smaller frame). It would be helpful to know where the 11-lever frame came from and where the 19-lever frame went.

Questions about when frames removed or abolished

15A. Frame at Great Central (now Marylebone). Frame originally in crows nest above Harewood Place crossover and moved to southbound platform when service extended to Edgware Road. Frame had gone by 1915 so far as it has been possible to tell, but exact date needed. Also useful to know where frame went as there were few spare frames at that time. Crossover almost certainly abolished at same time.

Questions about particular frames

16. Frame at Colindale (15 lever Style K No E22) was burnt out in August 1935. The signalbox was reopened in April 1936 with a metal-clad Style B or K frame also of 15 levers. There is no immediate evidence a new frame was ordered, so the question is whether the original frame was rebuilt or whether it was scrapped and a refurbished frame recovered from somewhere else was deployed. Do we know which and if a recovered frame then where did it come from?

17. Frame at South Woodford (35 lever Style N) was taken out of service in 1972 but remained on site. A 1990 photo shows that half of it (maybe 15-19 levers or so) was still there in 1990, though clearly out of use (levers all over the place and probably all jammed). The high end levers remained and the floor where the left hand section had been was plated over. The left hand panelling had been properly put back over the shortened section of frame. Why would any of this have been done, and when, and when did final section get removed?

17A. When Paddington Arrivals (GWR) BPSCo frame burnt out in 1938 the LTPB are reputed to have supplied a Style N interlocking to replace it on a temporary basis. The view seems to be that the 'suburban' lines section was catered for by the 59-lever frame intended for Aldgate (No 183) but not then installed. Historian Alan Jackson has stated that the LPTB supplied equipment totalling 141 levers in all, suggesting an 83 lever frame was also borrowed for the GWR's main line section (or more than one frame totalling this number). The questions are (a) was Aldgate borrowed and used for this purpose, and (b) what other frame or frames were borrowed (if any) to help out GWR, where did they come from and to where were they returned? Any information about this fairly major effort to help out would be of interest.

17B. The frame at Mansion House was definitely a 35-lever Style B on installation in 1906, nearly all levers in use. Following track alterations in 1911, only 11 levers were in use (but still in old frame). By 1931 signals and points renumbered in range 1-11, so possible frame had been exchanged for an 11-lever frame. In 1939 a crossover installed, taking numbering up to 15, but instructions refer to 'an 11-lever section' having been added. This suggests frame now 23-levers. However staff recall working frame and are confident it was just 15-levers. Questions are therefore (a) was frame changed from 35-levers to a smaller one, and if so when (surmise it was between 1911 and 1917), and (b) what was actually done in 1939 (additional 11-levers, or 4-levers or was frame actually changed), and (c) were there any other changes between 1939 and when frame superseded by an IMR, and if so, what?

Questions about outdoor equipment

18. The Northern Line Edgware branch (north of Golders Green to Edgware) was originally equipped with all-electric equipment (1923-24). When was it equipped with an air main and with pneumatic points and trainstops? This appears to have been sometime after 1952.

19. The Metropolitan Line Stanmore branch (Stanmore Junction [north of Wembley Park] to Stanmore) was originally equipped with all-electric equipment (1932/37). When was it equipped with an air main and with pneumatic points and trainstops?

20. The Metropolitan Line layout at Baker Street was originally equipped with all-electric equipment (1924). When was it equipped with an air main and with pneumatic points and trainstops?

Questions about signalbox locations

21. Where was the intended signal box at the new Kings Cross (Metropolitan Line) station to have been? The station actually opened slightly earlier than intended on 14 March 1941, and the signal box intended to work the bay connections must have been at least partly constructed by then. The frame was intended to be a 35-lever Westinghouse Style N frame, number 202. Was it ever installed (we know it was never commissioned)? Do we know where frame 202 ended up?

21A. Now answered, thank you. Had been about location of Tooting Broadway frame. See A13.

Non power frame questions

22. When was the M&GC line signalbox at Verney Junction withdrawn from service as a signal box? The line was singled in January 1940 and a 1941 LMSR plan suggests that the few running signals still needed for M&GC operations had been transferred to the control of the LMS box with ground frames at each end of the Verney yard to control access (the east end frame operated by a key on the train token and the west frame released by the LMSR box). Were these ground frames new or was the west frame really the old signalbox, whose structure lasted until the 1950s?

23. Exact closure date of Dutchlands Signal Box (and a more precise opening date) would be very helpful.

24. What kind of frame was there at Charing Cross (District Line) station (subsequently Embankment) until it was replaced in 1968, and how many levers was it?

25. Opening date of Harrow Yard (sometimes Harrow North) signal box. Alan Jackson, in London's Metropolitan Railway, page 146, states this box opened in 1900. However, Harrow goods yard was there somewhat earlier (believed from station opening) and had running connections far too far away to be worked by station box; a signal box is also shown as open on 1897 1:2500 OS mapping, in same position as box found later. Any clarification of events here prior to 1901 would be very welcome, particularly opening date with references.

26. It has been suggested that in the early 1950s, south of Aylesbury on the M&GC line near the Mandeville Road bridge, there was a ground frame at the southern exit of the up side sidings. I have found no reference to this on official diagrams. Does anyone have any information about a GF at this location?

27. Answered - had been about Brent North. See A12. Thank you..

The above questions are very specific because the author probably has a certain amount of information already. However, if you can answer any of the questions or have any other observations to make then the author would be delighted to hear from you. Please use the button below to start off an email. The questions are likely to change over time, and more are on way.

Answers to recent questions posed

A1. London Bridge frame was 11 lever B frame and subsequently recovered for use at RTC in 1962. (Immediate Source LT Magazine). This frame appears to have been recovered from Mornington Crescent for re-installation at London Bridge in 1924. (Source frame number and appearance). 1924 signal box was located at south end of northbound platform with back of frame situated against station headwall (source signalman who worked there and signalling notice).

A2. Gloucester Road (Met frame 1952) was a 15 lever B frame and photograph of it now seen. (Immediate Source a former signalman and researcher)

A3. Bank (Central Line 1958) was an 11 lever 'N' frame reputed to have been part of Wembley Park following frame shortening. This was of course really an L frame but an N was substantially the same parts as an L but with mechanical locking which had been added (Anecdotal from former signalman who worked there and who was told by lineman at Bank when he worked there).

A4. Queensway was 11 lever N frame (several sources). It is understood that it was another recycled section from Wembley Park (there are 3 x 12-lever sections to account for and this would make second of the three). Frame type from two sources (a signalman and a signal engineer). Box located east end of EB, next to siding.

A5. St James's Park - information so far suggests this was a style 'B' frame, though no photo or documentation yet seen. (Immediate source a former LT signal engineer)

A6. Hounslow West was an 11-lever Style N frame. (Immediate sources of frame type a former signal engineer and a former signalman and photos seen). Provenance unknown (there was a suggestion it came from Moorgate CWL, presumably the temporary box, but this must have been 15-lever and certainly more than 11).

A7. Finchley Central temp box location now known on top of embankment on NB side (photographs seen). Further update - from several reports and a photo there is now consensus temporary frame was a 23-lever Style N frame. Was question 9.

A8. Kennington (cabin code B) temporary box between 22 September 1957 and 25 January 1958 was a Style B frame of 23 levers. Was question 5.

A9. I now have a date for replacement interlocking at West Ruislip (register updated) Was question 101.

A10. I now have a reasonably good date for closure of Dutchlands signal box (register updated). Was question 23. This has been left on site in case someone can provide something even better.

A11. Holborn. The temporary frame used on Piccadilly Line between 15 July 1979 and 1 March 1980 was a Style N, later recovered and now used on the Acton Miniature Railway. Outstanding (Question 8) is where it was before use at Holborn (register updated). Was question 8.

A12. Brent North. Answer given for this indicates it was a Met box that closed 21st May 1967 at which time it had 20 levers. Was Question 27. Info from SRS Signal Box Register - vol. 3 (G.N., G.E & G.C.)

A13. I had a query about the exact location of Tooting Broadway cabin (W), known to be at south end of the station. The following appears to clarify the matter. The door at the south end of the northbound platform led to a narrow passage sloping downwards that led in to a tunnel-diameter sized passage between the running tunnels. The first part of this is now unused with the rest of it being the IMR. The first part has/had a black and white tile floor apart from a rectangular area in the middle that showed where the lever frame would have been until the IMR. There is/was no access from this area to the SB platform. I subsequently clarified that the frame was in this first section (with chequered floor) and the relay room was in the rear part. Was Question 21A. Info from David Churchill at LU. Thanks.