NOTE: Dates given are for trolleybus production only, some firms started as omnibus producers before entering TB production and some are still operating today.

INDEPENDENT CHASSIS MANUFACTURERS
    RAILLESS ELECTRIC TRACTION            Bristol                1908  to  1927            Imported until 1922
    ALLDAYS AND ONIONS                           Birmingham       1911  to  Pre 1930
    DAIMLER                                                      Covertry             1915  to  1949
    EMB LIMITED                                                                           1924  to  1924           Built only one trolleybus
    RANSOMES SIMES AND JEFFERIES      Ipswich               1924  to  1939
    TILLING-STEVENS                                       Maidstone         1924  to  1936
    GARRETT                                                       Leiston               1925  to  1930
    THORNTCROFT                                                                        1932  to  1932           Built on one trolleybus
    SCAMMELL LORRIES LIMITED                                           1964  to  1964           See note A
    QUEST 80 LIMITED                                                                  1980  to  1980           Built only one trolleybus for Johannesburg, South Africa
    DENNIS                                                                                       1985  to 1985            Built only one trolleybus for South Yorkshire Transport
 

THE GROUPS
THE ROOTES GROUP OF COMPANIES (1931 TO 1962)
The Rootes group started out as independent company in 1931 and began to acquired smaller independent companies from 1934 onwards

    STRAKER-SQUIRES                                                                 1912  until                 Merged 1921 with Cloughs to form:-
    STRAKER-CLOUGHS                                                               1921  until                 Merged 1931 with Karrier to form:-
    GUY                                                                                              1926                           Taken over by the Roots Group in 1948
    KARRIER-CLOUGHS                                                                1931                           Taken over by the Roots Group in 1934
    SUNBEAM (original company)                                             1931  to 1962

BRITISH LEYLAND GROUP OF COMPANIES (1927-1958)
British Leyland group started out as independent company known as Leyland Motor Works  in 1927 and began to acquired smaller independent companies from 1946 onwards

    ASSOCIATED EQUIPMENT COMPANY                             1922  until                 Merged with Leyland 1946 to form BUT
    LEYLAND MOTOR WORKS  (original company)             1927                           Merged its trolleybus section 1946 with AEC to form BUT
    ENGLISH ELECTRICS                                                               1928                           See note B
    CROSSLEY                                       Manchester                      1936  until                 Taken over by British United Traction in 1954
    BRITISH UNITED TRACTION     Lancashire                        1946  to  1958           See note C

SPECIAL NOTES:
    A    Scammell Lorries Ltd picked up the  Wellington, New Zealand contract from Leyland following the closure of their trolleybus plant.
           The 37 trolleybuses (Nos 82 to 119)  were built on Scammell chassis making them not a true Leyland, although they do contain
           some Leyland parts.

    B    English Electrics were the main supplier of electrical equipment to Leyland. Following up-surge in the popularity of the trolleybus in
           the twenties, were sub-contracted by Leyland to build trolleybus chassis to help clear back log. These trolleybuses were officially
           known as Leyland-English Electrics. In all, less than 150 were built, six of which were sold to the Christchurch Tramway Board,
           New Zealand in 1931. English Electrics were taken over completely by Leyland in 1934, when the name was dropped from the
           trolleybus scene.

    C    Although Leyland, under the banner of BUT, finished trolleybus production in 1958, they did, under the name British Leyland
          supply trolleybus chassis using the Atlantean diesel to Oporto, Portugal in 1967, and to Arnhem, Holland in 1969. British Leyland
          gave a contract to Scammell Lorries Limited they won in 1962 for Wellington CityCouncil, New Zealand.

Source of information
        History of the British Trolleybus by Nicholas Owen, published by David and Charles, 1974
        Trolleybuses in New Zealand, by Sean Millar, published by Milar Publishing, 1986
        Trolleybus Magazine, Journal of the National Trolleybus Association, various issues 1980-1989
        Leyland Motors Limited, Lancashire