Last update 14 November 2008
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Introduction A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Non-National Rail
Phil Deaves, Swindon, Wiltshire
I am always grateful for additional information, whether entirely new records (particularly historical records), or information to fill in gaps or correct errors, via the email address above. Thank you.
Although the Docklands Light Railway is an automated system, trains are driven manually in the depots. At present, only two signal codes are known, both for Poplar depot. These are AS and WA.
Most signals appear not to carry a prefix. Those seen with a prefix carry A.
London Underground (and its predecessors) has a complex signal labelling system. A summary can be found below, most of the raw data coming from District Dave's site (Page 1, Page 2, Page 3), and from Tube Prune (these sources are not identical), in addition to other observations. In addition to these codes, a 1930s photograph shows signals at Stanmore (controlled from Wembley) displaying Y8LA and Y4LA on the same post. The Y represents control from Stanmore, and the L signifies "push-pull lever control". The significance of the smaller A is not known.
| Code | Control centre or relay room | Current Line (for numbering series purposes) | Date code used (where known) | Became or taken over by (where known) |
|---|---|---|---|---|
| BMX | "Special" signal | Bakerloo | - | |
| A | Automatic signals | [General use] | - | |
| S | Automatic signals | Northern | - | |
| X | Last automatic signal before controlled area (also used in combination with controlled area code) | [General use] | - | |
| FDX | Floodgate signals | District | - | |
| FNX | Floodgate signals | Northern | - | |
| FX | Floodgate signals | Victoria | 1968- | - |
| TN | Floodgate signals (at Canning Town) | Jubilee | 1999- | - |
| X | Floodgate signals | Bakerloo | - | |
| PNX | Possession protection signals | Northern | - | |
| WL | Acton Town | District | 1905- | - |
| E | Aldersgate (Barbican) | Metropolitan/Circle | 1865-1954 | OG |
| P | Aldersgate (Widened Lines) | Metropolitan/Circle | 19xx-1924 | E |
| H | Aldgate | Metropolitan/Circle | 1909-1946 | OB |
| OB | Aldgate and Aldgate East | Circle | 1946- | - |
| EL | Aldgate East | District | 1906-1946 | OB |
| JW | Amersham | Metropolitan | 1960- | - |
| K | Angel | Northern | 1919-1959 | - |
| J | Arnos Grove | Piccadilly | 1932-1982 | PJ |
| PJ | Arnos Grove | Piccadilly | 1982- | - |
| BM | Baker Street | Jubilee | 1939- | - |
| MB | Baker Street | Metropolitan | 1947- | - |
| M | Baker Street | Metropolitan/Circle | 1928-1947 | MB |
| A | Baker Street (also recorded as B in some sources) | Metropolitan/Circle | 1913-1928 | M |
| B | See Baker Street (A) | |||
| B | Bank | Central | 1914-1941 | CB |
| BAN | Bank | Central | 1996- | - |
| CB | Bank | Central | 1941-1971 | - |
| OG | Barbican | Circle | 1954-1979 | - |
| FF | Barking And Upney | District | 1960- | - |
| BAR | Barkingside | Central | 1996- | - |
| LN | Barkingside Ground Frame | Central | 1948-1965 | - |
| WC | Barons Court | District | 1962-1983 | - |
| WD | Barons Court | District | 1906- | - |
| TR | Bermondsey | Jubilee | 1999- | - |
| BEG | Bethnal Green | Central | 1995- | - |
| LC | Bethnal Green | Central | 1946-1995 | - |
| LY | Blake Hall Ground Frame (no signals present) | Central | 1957-1967 | - |
| X | Borough | Northern | 1922-1923 | - |
| WS | Boston Manor | District | 1974- | - |
| EP | Bow Road | District | 1907-1964 | - |
| AA | Brent Cross | Northern | 1926-1937 | - |
| C | British Museum | Central | 1914-1933 | CB |
| VE | Brixton | Victoria | 1971- | - |
| FB | Bromley-By-Bow | District | 1960- | - |
| FBX | Bromley-By-Bow advanced starting board | District | 1960- | - |
| FRFB | Fog repeater for Bromley-By-Bow signals | District | 1960- | - |
| FRFBX | Fog repeater for Bromley-By-Bow intermediate stop signals | District | 1960- | - |
| RFB | Repeater for Bromley-By-Bow advanced signals | District | 1960- | - |
| RFBX | Repeater for Bromley-By-Bow advanced starting board | District | 1960- | - |
| BUH | Buckhurst Hill | Central | 1996- | - |
| LS | Buckhurst Hill Ground Frame | Central | 1948-1965 | - |
| BT | Camberwell Green (planned, not used) | Bakerloo | - | - |
| E | Camden Town | Northern | 1907- | - |
| TK | Canada Water | Jubilee | 1999- | - |
| E | Canal Junction | East London | 1913-1950 | ET |
| RE | Repeater for Canal Junction signals | East London | 1913-1950 | ET |
| ET | Canal Junction | East London | 1950-1997 | - |
| RF | Canal Junction | Proposed Fleet Line/East London | - | - |
| TL | Canary Wharf | Jubilee | 1999- | - |
| MJ | Canons Park | Metropolitan | 1941-1976 | - |
| WW | Canons Park | Metropolitan | 1941-1941 | MJ |
| JT | Chalfont | Metropolitan | 1949-1959, 1960- | JW |
| JW | Chalfont | Metropolitan | 1959-1960 | JT |
| CHL | Chancery Lane | Central | 1996- | - |
| TG | Charing Cross | Jubilee | 1978- | - |
| C | Charing Cross | Northern | 1937- | - |
| RC | Charing Cross | Proposed Fleet Line/East London | - | - |
| JV | Chesham | Metropolitan | 1949-1970 | - |
| CHI | Chigwell | Central | 1996- | - |
| JS | Chorleywood | Metropolitan | 1954-1970 | - |
| T | Clapham Common | Northern | 1919-1976 | - |
| M | Cockfosters | Piccadilly | 1933-1982 | PM |
| PM | Cockfosters | Piccadilly | 1982- | - |
| AC | Colindale | Northern | 1924- | - |
| B | Covent Garden | Piccadilly | 1906-1931 | C |
| C | Covent Garden | Piccadilly | 1931-1979 | - |
| EC | Cromwell Road | District | 1906-1967 | - |
| B | Croxley | Metropolitan | 1924-1970 | - |
| FG | Dagenham East | District | 1960- | - |
| DEB | Debden | Central | 1996- | - |
| LU | Debden | Central | 1949-1996 | DEB |
| D | Deptford Road Junction (GF emergency crosover) | East London | 1913-1950 | - |
| MX | Dollis Hill | Metropolitan | 1938-1939 | - |
| PB | Down Street | Piccadilly | 1979- | - |
| LD | Drapers Field (Leyton) (temporary reversing siding) | Central | 1946-1947 | - |
| B | Drayton Park | Northern City | 1904-1953 | NC |
| NC | Drayton Park and Finsbury Park | Northern City | 1939-1976 | - |
| EAB | Ealing Broadway | Central | 1993- | - |
| L | Ealing Broadway | Central | 1920-1952 | WP |
| WP | Ealing Broadway | District | 1905- | - |
| WM | Ealing Common | District | 1905- | - |
| EC | Earls Court (Main) | District | 1966- | - |
| EA | Earls Court East | District | 1905-1936 | EC |
| WA | Earls Court West | District | 1905-1966 | EC |
| EAA | East Acton | Central | 1996- | - |
| MS | Eastcote (also recorded as MR in some sources) | Metropolitan | 1948-1966 | - |
| MR | See Eastcote (MS) | |||
| T | Eastcote (also recorded as R in some sources) | Metropolitan | 1930-1948 | MS |
| R | See Eastcote (T) | |||
| NP | East Finchley | Northern | 1939-1961 | - |
| FE | East Ham | District | 1960- | - |
| FEX | East Ham last automatic signal before controlled area | District | 1960- | - |
| FD | East Ham (planned, not used) | District | - | - |
| AE | Edgware | Northern | 1924- | - |
| A | Edgware Road | Bakerloo | 1907-1913 | - |
| B | Edgware Road | Metropolitan/Circle | 1907-1951 | OP |
| OP | Edgware Road | Metropolitan/Circle | 1951- | - |
| BS | Elephant And Castle | Bakerloo | 1941-1991 | - |
| E | Elephant And Castle | Bakerloo | 1906-1941 | BS |
| Q | Elephant And Castle? | Northern | - | |
| EH | Embankment | District | 1905- | - |
| EPP | Epping | Central | 1996- | - |
| LW | Epping | Central | 1949-1996 | - |
| J | Euston | Northern | 1919- | - |
| OZ | Euston Square | Metropolitan/Circle | 1941-19xx | - |
| FAI | Fairlop | Central | 1996- | - |
| LM | Fairlop Ground Frame | Central | 1948-1964 | - |
| D | Farringdon | Metropolitan/Circle | 1909-1956 | OH |
| OH | Farringdon | Metropolitan/Circle | 1956- | - |
| M | Farringdon (Widened Lines) | Metropolitan/Circle | 19xx-1924 | D |
| RD | Fenchurch Street | Proposed Fleet Line/East London | - | - |
| NQ | Finchley Central | Northern | 1940-1969 | - |
| JD | Finchley Road | Jubilee | 1984- | - |
| MD | Finchley Road | Metropolitan | 1937- | - |
| C | Finchley Road (also recorded as D) | Metropolitan | 1911-1937 | MD |
| D | See Finchley Road (C) | |||
| C | Finsbury Park | Northern City | 1904-1939 | NC |
| F | Finsbury Park | Piccadilly | 1906-1965 | VK |
| VK | Finsbury Park | Victoria | 1968- | - |
| GAH | Gants Hill | Central | 1996- | - |
| EE | Gloucester Road/South Kensington | District | 1906-1957 | EC |
| K | Gloucester Road | Metropolitan/Circle | 1909-1952 | OQ |
| OQ | Gloucester Road | Metropolitan/Circle | 1952-1957 | EC |
| G | Golders Green | Northern | 1907- | - |
| GRH | Grange Hill | Central | 1997- | - |
| LK | Grange Hill (subsiduary to Hainault) (unofficial code), also recorded as LL | Central | 1948-1997 | GRH |
| B | Great Central (Marylebone) | Bakerloo | 1907-1915 | - |
| TF | Green Park | Jubilee | 1999- | - |
| CL | Greenford | Central | 1947-1960 | - |
| CLX | Greenford | Central | 1947-1948 | - |
| GRE | Greenford | Central | 1996- | - |
| HAI | Hainault | Central | 1997- | - |
| LL | Hainault/Grange Hill | Central | 1948-1997 | - |
| H | Hammersmith | Hammersmith and City | 1921-1951 | OZ |
| OZ | Hammersmith | Hammersmith and City | 1951- | - |
| A | Hammersmith | Piccadilly | 19xx-1932 | WD |
| F | Hampstead | Northern | 1907- | - |
| HAL | Hangar Lane | Central | 1996- | - |
| WO | Hanger Lane Junction (also recorded as WN) | District | 1905-1925 | WM |
| WN | See Hanger Lane Junction (WO) | |||
| N | Harrow North | Metropolitan | 1908-1948 | JB |
| H | Harrow South | Metropolitan | 1908-1948 | JB |
| J | Harrow Station | Metropolitan | 1908-1948 | JB |
| JB | Harrow-on-the-Hill | Metropolitan | 1948- | - |
| WW | Hatton Cross | Piccadilly | 1975- | - |
| WY | Heathrow Central | Piccadilly | 1977- | - |
| AB | Hendon Central | Northern | 1923-1930 | - |
| NU | High Barnet | Northern | 1940- | - |
| VJ | Highbury | Victoria | 1968- | - |
| H | Highgate (Archway) | Northern | 1907-1939 | NN |
| NN | Highgate (Archway) | Northern | 1939- | - |
| NH | Highgate Depot Panel | Northern | 1989- | - |
| EB | High Street Kensington | District | 1907-1936 | - |
| ED | High Street Kensington | District | 1967- | - |
| J | High Street Kensington | Metropolitan | 1909-1926 | EB |
| MV | Hillingdon | Metropolitan | 1948-1966 | - |
| V | Hillingdon | Metropolitan | 1930-1948 | MV |
| C | Holborn | Central | 1933-1941 | CC |
| CC | Holborn | Central | 1941-1994 | HOL |
| HOL | Holborn | Central | 1994- | - |
| D | Holborn/Aldwych | Piccadilly | 1906-1980 | PD |
| PD | Holborn/Aldwych | Piccadilly | 1980- | - |
| HOP | Holland Park | Central | 1996- | - |
| FJ | Hornchurch | District | 1959- | - |
| FK | Hornchurch | District | 19xx-1959 | FJ |
| WT | Hounslow Central | District | 1910- | - |
| WS | Hounslow East/Town | District | 1905-1923 | - |
| WX | Hounslow West | District | 1926-1975 | - |
| WT | Hounslow West/Barracks | District | 19xx-c1905 | - |
| A | Hyde Park Corner | Piccadilly | 1906-1931 | B |
| B | Hyde Park Corner | Piccadilly | 1931-1979 | PB |
| WH | Junction with LWSR at Ravencscourt Park? | District | - | |
| A | Kennington | Northern | 1926-1937 | B |
| B | Kennington | Northern | 1937- | - |
| Y | Kennington (temporary control) | Northern | 1923-19xx | - |
| D | Kennington Road (Lambeth North) | Bakerloo | 1906-1939 | BR |
| OJ | Kings Cross | Metropolitan | 1941- | - |
| C | King's Cross | Metropolitan/Circle | 1908-1958 | OJ |
| J | King's Cross | Metropolitan/Circle | 1912-1939 | - |
| L | King's Cross | Northern | 1927- | - |
| VH | King's Cross | Victoria | 1968- | - |
| E | Ladbroke Grove | Hammersmith and City | 1921-1950 | OU |
| OU | Ladbroke Grove | Hammersmith and City | 1950-1983 | - |
| BR | Lambeth North | Bakerloo | 1939-1991 | - |
| LAG | Lancaster Gate | Central | 1996- | - |
| F | Latimer Road | Hammersmith and City | 1921-1950 | OV |
| OV | Latimer Road | Hammersmith and City | 1950-1957 | - |
| RK | Lewisham | Proposed Fleet Line/East London | - | - |
| LE | Leyton | Central | 1947-1971 | - |
| LEY | Leyton | Central | 1996- | - |
| LES | Leytonstone | Central | 1997- | - |
| LF | Leytonstone | Central | 1947-1997 | - |
| A | Liverpool Street | Central | 1912-1937 | LB |
| LB | Liverpool Street | Central | 1937-1997 | LIS |
| LIS | Liverpool Street | Central | 1997- | - |
| G | Liverpool Street | Circle | 1910-1954 | OD |
| OD | Liverpool Street | Circle | 1954- | - |
| TJ | London Bridge | Jubilee | 1999- | - |
| P | London Bridge | Northern | 1919- | - |
| D | London Road Depot | Bakerloo | 1906-1915 | D |
| B | Lords | Metropolitan | 1910-1937 | MC |
| MC | Lords | Metropolitan | 1937-1971 | ML |
| LOU | Loughton | Central | 1997- | - |
| LT | Loughton | Central | 1948-1997 | - |
| EG | Mansion House | District | 1973- | - |
| EI | Mansion House | District | 1969-1973 | EG |
| CD | Marble Arch | Central | 1941-1994 | MAA |
| D | Marble Arch | Central | 1914-1941 | CD |
| MAA | Marble Arch | Central | 1994- | - |
| MIE | Mile End | Central | 1996- | - |
| NV | Mill Hill East Ground Frame | Northern | 1943-1964 | - |
| EK | Minories Junction | District | 1906-1909 | EL |
| D | Moor Park | Metropolitan | 1924-1953 | - |
| JG | Moor Park | Metropolitan | 1962-1971 | - |
| OE | Moorgate | Circle | 1956- | - |
| F | Moorgate | Metropolitan/Circle | 1909-1956 | OE |
| M | Moorgate | Northern | 1919- | - |
| A | Moorgate | Northern City | 1904-1922 | D |
| D | Moorgate | Northern City | 1922-1937 | ND |
| ND | Moorgate | Northern City | 1937-1976 | - |
| R | Moorgate (Widened Lines) | Metropolitan/Circle | 19xx-1926 | F |
| Y | Morden | Northern | 1926- | - |
| Z | Morden Depot Ground Frame (unofficial code) | Northern | 1926- | - |
| D | Mornington Crescent | Northern | 1907-1924 | E |
| JM | Neasden | Jubilee | 1985- | - |
| F | Neasden | Metropolitan | 1911-1938 | MF |
| MM | Neasden | Metropolitan | 1985- | - |
| JF | Neasden (some doubt if this code used) | Jubilee | 1985- | - |
| MH | Neasden North | Metropolitan | 1939-1987 | - |
| MF | Neasden South | Metropolitan | 1938-1987 | MM |
| RJ | New Cross | Proposed Fleet Line/East London | - | - |
| RH | New Cross Gate | Proposed Fleet Line/East London | - | - |
| LP | Newbury Park | Central | 1947-1994 | NEP |
| NEP | Newbury Park | Central | 1994- | - |
| CJ | North Acton | Central | 1947-1996 | NOA |
| K | North Acton | Central | 1920-1947 | CJ |
| NOA | North Acton | Central | 1996- | - |
| WU | North Ealing | District | 1907-1971 | - |
| TM | North Greenwich | Jubilee | 1999- | - |
| LX | North Weald | Central | 1957-1978 | - |
| WR | Northfields | District | 1916- | - |
| CP | Northolt | Central | 1960-1996 | - |
| NOR | Northolt | Central | 1996- | - |
| VN | Northumberland Park | Victoria | 1968- | - |
| E | Northwood | Metropolitan | 1924-1962 | JF |
| JF | Northwood | Metropolitan | 1962-1962 | - |
| F | Northwood Hills Siding Ground Frame | Metropolitan | 1924-1953 | - |
| JE | Northwood Hills Temporary Box | Metropolitan | 1961-1962 | - |
| NHG | Notting Hill Gate | Central | 1996- | - |
| K | Oakwood | Piccadilly | 1933-1982 | PK |
| PK | Oakwood | Piccadilly | 1982- | - |
| L | Old Street | Northern City | 1919-1922 | - |
| LZ | Ongar | Central | 1957-1969 | LX |
| WR | Osterley Park | District | 19xx-1910 | - |
| OXC | Oxford Circus | Central | 1996- | - |
| BD | Paddington | Bakerloo | 1939- | - |
| C | Paddington | Bakerloo | 1913-1939 | BD |
| OR | Paddington Suburban (some doubt whether code used) | Circle | - | |
| NH | Park Junction | Northern | 1939-1984 | - |
| WF | Parsons Green | District | 1905- | - |
| PER | Perivale | Central | 1996- | - |
| B | Piccadilly Circus | Bakerloo | 1915-1939 | BP |
| BP | Piccadilly Circus | Bakerloo | 1939- | - |
| BPZ | Piccadilly Circus station starting signals (controlled from Bakerloo cabin) | Piccadilly | 1939-1980 | - |
| BZ | Piccadilly Circus station starting signals (controlled from Bakerloo cabin) | Piccadilly | 1934-1939 | BPZ |
| Y | Piccadilly Circus station starting signals (controlled from Bakerloo cabin) | Piccadilly | 1915-1927 | - |
| G | Pinner | Metropolitan | 1924-1962 | JD |
| JD | Pinner | Metropolitan | 1962-1970 | - |
| FC | Plaistow | District | 1959-7 May 1960 | - |
| FCX | Plaistow last automatic signal before controlled area | District | 1959-7 May 1960 | - |
| A | Praed Street Junction | Metropolitan/Circle | 1908-1926 | B |
| MZ | Preston Road | Metropolitan | 1938-1948 | - |
| WG | Putney Bridge | District | 1905- | - |
| A | Queens Park | Bakerloo | 1915-1937 | BB |
| BB | Queens Park | Bakerloo | 1937- | - |
| CE | Queens Road (Queensway) | Central | 1941-1984 | - |
| E | Queens Road (Queensway) | Central | 1914-1941 | CE |
| QUE | Queensway | Central | 1996- | - |
| MP | Rayners Lane | Metropolitan | 1985- | - |
| P | Rayners Lane | Metropolitan | 1925-1985 | MP |
| REB | Redbridge | Central | 1996- | - |
| JP | Rickmansworth | Metropolitan | 1953- | - |
| K | Rickmansworth | Metropolitan | 1910 or 1924-1953 | JP |
| ROV | Roding Valley | Central | 1996- | - |
| RE | Rotherhithe/Surrey Docks | Proposed Fleet Line/East London | - | - |
| X | Royal Oak (special signals activated by derailment detector in main line goods yard) | Hammersmith and City | 1970-1978 | - |
| MT | Ruislip | Metropolitan | 1948-1975 | - |
| U | Ruislip | Metropolitan | 1930-1948 | MT |
| RUG | Ruislip Gardens | Central | 1993- | - |
| MU | Ruislip Siding | Metropolitan | 1975- | - |
| EG | St James's Park | District | 1905-1967 | - |
| EM | St Marys Junction (planned, not used) | District | - | - |
| STP | St Paul's | Central | 1996- | - |
| VL | Seven Sisters | Victoria | 1968- | - |
| CF | Shepherd's Bush | Central | - | |
| F | Shepherd's Bush | Central | 1914-1938 | - |
| SHB | Shepherd's Bush | Central | 1996- | - |
| A | Shoreditch | East London | 1913-1928 | - |
| B | Shoreditch/Whitechapel | East London | 1943-19xx | - |
| N | Smithfield (Widened Lines) | Metropolitan/Circle | 1909-1918 | PK |
| SNA | Snaresbrook | Central | 1996- | - |
| LG | Snaresbrook Ground Frame | Central | 1947-c1954 | - |
| WQ | South Acton | District | 1905-1932 | - |
| WV | South Harrow | District | 1932- | - |
| EF | South Kensington | District | 1967- | - |
| L | South Kensington | Metropolitan | 1909-1949 | OR |
| OR | South Kensington | Metropolitan | 1949-1957 | EC |
| SOR | South Ruislip | Central | 1996- | - |
| LH | South Woodford | Central | 1947-1972 | - |
| SOW | South Woodford (George Lane) | Central | 1996- | - |
| TP | Southwark | Jubilee | 1999- | - |
| JL | Stanmore | Jubilee | 1984- | - |
| MK | Stanmore | Bakerloo | 1938-1986 | JL |
| Y | Stanmore | Metropolitan | 1932-1938 | - |
| U | Stockwell | Northern | 1919-1962, 1976- | - |
| B | Strand | Northern | 1907-1937 | C |
| C | Strand/Charing Cross | Northern | 1937- | - |
| TW | Stratford | Jubilee | 1999- | - |
| LD | Stratford (some doubt if code used) | Central | - | |
| TY | Stratford Market Depot | Jubilee | 1999- | - |
| WW | Sudbury Hill | District | 1933-1966 | - |
| C | Surrey Docks | East London | 1913-1950 | ER |
| ER | Surrey Docks/Quays | District | 1950- | - |
| ML | Swiss Cottage | Metropolitan | 1964- | - |
| THB | Theydon Bois | Central | 1996- | - |
| LV | Theydon Bois Ground Frame | Central | 1949-1967 | - |
| W | Tooting Broadway | Northern | 1926- | - |
| TCR | Tottenham Court Road | Central | 1996- | - |
| NT | Totteridge Ground Frame | Northern | 1940- | - |
| EJ | Tower Hill | District | 1967- | - |
| WK | Turnham Green | District | 1911- | - |
| FM | Upminster | District | 1958- | - |
| MW | Uxbridge | Metropolitan | 1938- | - |
| W | Uxbridge | Metropolitan | 1930-1938 | MW |
| VF | Victoria | Victoria | 1969- | - |
| VP | Walthamstow Central | Victoria | 1968- | - |
| WAN | Wanstead | Central | 1996- | - |
| VG | Warren Street | Victoria | 1968- | - |
| BR | Waterloo | Bakerloo | 1991- | - |
| BS | ||||
| TH | Waterloo | Jubilee | 1999- | - |
| A | Watford | Metropolitan | 1924-1948 | JL |
| JL | Watford | Metropolitan | 1948-1958 | JP |
| C | Watford Junction (Croxleyhall) | Metropolitan | 1924-1955 | JP |
| JJ | Watford South Junction (Croxleyhall) | Metropolitan | 1962- | - |
| JG | Wembley Park | Jubilee | 1984- | - |
| G | Wembley Park | Metropolitan | 1911-1937 | MG |
| MG | Wembley Park | Metropolitan | 1937- | - |
| WEA | West Acton | Central | 1996- | - |
| D | Westbourne Park | Hammersmith and City | 1921-1950 | OS |
| OS | Westbourne Park | Hammersmith and City | 1950-1971 | - |
| WE | West Brompton | District | 1906-1971 | - |
| WEH | West Ham | Central | 1996- | - |
| TU | West Ham/Stratford (West end) | Jubilee | 1999- | - |
| D | West Hampstead | Metropolitan | 1911-1937 | MD |
| WB | West Kensington East and Olympia | District | 1906- | - |
| WC | West Kensington West | District | 1906- | - |
| WER | West Ruislip | Central | 1991- | - |
| CS | West Ruislip/Ruislip Gardens | Central | 1948-1991 | WER |
| CG | White City | Central | 1948-2000 | WHC |
| WHC | White City | Central | 1996- | - |
| EN | Whitechapel | District | 1907- | - |
| B | Whitechapel | East London | 1913- | EN |
| Q | Whitecross Street (Widened Lines) | Metropolitan/Circle | 19xx-1916 | P |
| E | Willesden Green | Metropolitan | 1911-1938 | ME |
| JE | Willesden Green | Jubilee | 1984- | - |
| ME | Willesden Green | Metropolitan | 1937-1985 | JE (in part) |
| WOO | Woodford | Central | 1997- | - |
| LJ | Woodford | Central | 1947-2000 | WOO |
| G | Wood Green | Piccadilly | 1932-1980 | PG |
| PG | Wood Green | Piccadilly | 1980- | - |
| G | Wood Lane | Central | 1914-1948 | CG |
| J | Wood Lane Junction | Central | 1920-1938 | - |
| NS | Woodside Park Ground Frame | Northern | 1940-1965 | - |
| E | York Road | Piccadilly | 1906-1964 | - |
Photographs seen suggest that most signals do not carry a prefix. Repeater signals carry R.
Prefixes for these are based on the electrification code, in addition to a P (points indicator) or S (stop signal). Other codes may also exist. Thus a stop signal at Phoenix Park carries the prefix PPS.
No evidence of any signal prefixes has been found.
Signal boxes without known prefixes are excluded.
| Code | Signal Box | Location | Note |
|---|---|---|---|
| A | Abergynolwyn | Talyllyn Railway | |
| A | Alston | South Tynedale Railway | |
| AT | Alton | Mid Hants Railway | |
| AR | Angel Road | Malden and District Society of Model Engineers | |
| AJ | Armwell Junction | East Herts Miniature Railway | |
| BJ | Bridgen Training Academy | Training signal | |
| B | Britannia Crossing | Paignton & Dartmouth Railway | |
| BC | |||
| CW | Cranmore West | East Somerset Railway | |
| DE | Deeside | Llangollen Railway | |
| KJ | Derby | Catalys Training | Training signal |
| R | East Lancashire Railway | Repeater signals | |
| GC | Grosmont Crossing | North Yorkshire Moors Railway | |
| H | Hampden Court Junction | Malden and District Society of Model Engineers | |
| H | Hythe | Romney Hythe & Dymchurch Railway | |
| CN | Ipswich | Rail Tech Group Training Academy | Training signal |
| F | Liverpool Overhead Railway | ||
| MA | Motala | Swanage Railway | |
| N | Needham | Stevington and Turvey Light Railway | |
| NB | New Bridge | North Yorkshire Moors Railway | |
| GF | Ground frame controlled signals | ||
| R | New Romney | Romney Hythe & Dymchurch Railway | |
| VO | Orchard Green Junction | Isle of Wight Railway | Museum demonstration signal |
| AF | Original code ("April Fool"), soon replaced | ||
| WJ | Rugby | Signalling Engineering School and Technical Assessment Centre (GM Rail Services) | Training signal |
| GM | |||
| ED | Slateford | Slateford Signalling School | Training signal |
| Z | South Kensington | London Underground Signalling School (in disused "deep level" tunnel) | Training signal |
| W | Willowbank | Malden and District Society of Model Engineers |
Introduction A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Non-National Rail