British Tabulating Machine Co
From Graces Guide
British Tabulating Machine Co (BTM), of Victoria House, Southampton Row, London, and Letchworth, Herts.
Telephone: Holborn 7866. Cables: "Tabulorial, Westcent, London". Factories at Letchworth, Herts.
1880s The origins of the company were in the punched-card machine technology invented by Herman Hollerith.
1896 Hollerith formed a small business in the United States to manufacture and market his machines.
British Tabulating Machine Co
1902 The Tabulator Limited was formed by Robert Porter who obtained rights from the US Tabulating Machine Company (or TMC) to sell Herman Hollerith's machines.
The Tabulator Limited was renamed the British Tabulating Machine Co Limited.
1908 The Tabulating Machine Company (TMC) gave an exclusive license to the British Tabulating Machine Co of London to market its punched-card machines in Britain and the Empire.
Hollerith had asked for £20,000, later lowering this to £10,000, for the licence to sell the tabulating machines in the UK and Europe. Porter failed to raise the required finance and offered instead £2000 plus a 25% royalty on all the revenues. TMC agreed to this but with the proviso that BTM could only hire out the machines. This was a poor deal for BTM. The market did not take off in Britain as it had in the USA, and it was not long before BTM were defaulting on their royalty payments to TMC.
1911 TMC became part of the Computing-Tabulating-Recording Co (C-T-R).
1911 BTM, of 2 Norfolk St, London WC2, made tabulating machines in accordance with the Hollerith patents for analyzing statistical information. Installed eight counting machines and fifteen sorting machines at Millbank for the 1911 census.
1920 BTM moved from London to Letchworth, Hertfordshire and started manufacturing its own machines, rather than simply reselling Hollerith equipment.
1921 Improved tabulating machines made for the Australian census
1924 C-T-R was renamed International Business Machines (IBM). The relationship between IBM and BTM worsened over the years.
By 1940, BTM’s biggest pre-war development project was the Rolling Total Tabulator and, being of British design, gave BTM a high level of technical independence from IBM.
During the early 1940s electronics had not yet become the main vehicle for solving intricate Business and Office Data Processing problems. Electro-mechanical solutions were still the main method by which problems were resolved and the techniques were well developed. These methods and techniques plus some very inventive minds existed in BTM and were quickly applied to the business of Code Breaking. Speed of implementation was also a strong attribute, which had been developed in dealing promptly with punched card customers needs. The first Turing Bombe was delivered to Bletchley Park in March 1940 in what was only a matter of months after the declaration of war.
WWII: Approximately 210 Turing Bombes were produced at Letchworth from 1940 to 1945 (in Letchworth these were more commonly known as 6/6502 or CANTAB machines).
By early 1945 the Bombe programme was winding down rapidly.
1947 Listed Exhibitor - British Industries Fair. Manufacturers of "Hollerith" Electrically Operated Punched Card, Tabulating and Accounting Equipment for the Mechanisation of all Accountancy Functions and the Compilation of Statistical and Scientific Figures. (Olympia, Ground Floor, Stand No. B.1435) 
1948 A factory was established at Castlereagh to manufacture the ancillary equipment to the tabulator.
1949 The oppressive agreement with IBM was dissolved but there was resistance in the company to use of the new electronics for calculators, which were based on electro-mechanical devices and therefore much more reliable.
c.1950 Concerned about the threat to its business from the emerging computer devices but recognising that IBM's CPC could not handle sterling arithmetic, the company recruited J. R. Womersley who had organised the Pilot ACE development at NPL. Womersley realised that other computers under development (in universities for scientific purposes) would be too big and too expensive for commercial use and had inappropriate memory technology. The company developed several prototypes - HEC 2 was demonstrated at Olympia in 1953.
The HEC 2 was then enhanced for commercial application, becoming known initially as the HEC 4, and later as the 1201. In total 125 1200s were supplied, more than any other British computer at the time
1961 GEC exited the arrangement with BTM to develop the 1301 computer but remained responsible for its manufacture.
The Turing Bombe was an electromechanical device used by British cryptologists to help break German Enigma machine signals during World War II. 
The name derived from a prototype developed by Polish code-breakers before the war, which they called a bombe. The bombe was a semi-mechanical device for working through the combinations of the wheels in the Enigma machine.
During the early 1940s electronics had not yet become the main vehicle for solving intricate business and office data processing problems. Electro-mechanical solutions were still the main method by which such problems were resolved and the techniques were well developed. These methods and techniques plus some very inventive minds existed in BTM and were quickly applied to the business of code breaking. Speed of implementation was also a strong attribute of this approach, which had been developed in dealing promptly with the needs of punched-card customers. The first Turing Bombe was delivered to Bletchley Park in March 1940 in what was only a matter of months after the declaration of war.
1940-1945 Approximately 210 Turing Bombes of all different types were produced at Letchworth from 1940 to 1945. Final assembly took place in the main BTM factory in Icknield Way. This factory later became known as 1/1 but has since been demolished to make way for a housing estate.
The first Bombes took six weeks to construct but, later, when built in batches of six, one came off the assembly line each week.
The Rolling Total Tabulator contained many ingenious British mechanisms and many of these in adapted form could be found in the Bombe design. However the incredible speed at which the first Bombe was developed did not allow for unnecessary design and development so where possible mechanisms from other punched-card equipment were used with minimal modification.
Sub-assemblies for the Bombes, including the frames were produced at other Letchworth factories - wiring at Spirella and engineering of the drums and other parts in the basement of the Ascot, Government Training Centre in Pixmore Avenue.
Security had to be as good at Letchworth as it was at Bletchley Park and although literally hundreds of people were involved in the Bombe production, the secret was kept, and the security was deliberately kept very low key. New Bombes were collected from the main factory loading ramp, visible from the main road, by a single soldier with an army lorry. He then set off to Bletchley Park or one of the Out-Stations without any form of escort. Nobody took any notice.
Whilst the general concepts of the Bombe were provided by Bletchley Park. It fell to the BTM design team at Letchworth in North Hertfordshire to design a practical machine.
The HEC4 (Hollerith Electronic Computer, fourth version) computer used thermionic valve technology; its main memory was drum storage. Input was from 80 column punched cards and output was to 80 column cards and a printer. After formation of International Computers and Tabulators, the computer was known as the ICT 1201
Sources of Information
-  BTM
- The Staffordshire University Computing Futures Museum Computers Page 
- The Engineer 1911/01/27
- The Engineer 1911/03/17
- The Engineer 1921/05/20
- 1947 British Industries Fair p44
- BTM's First Steps Into Computing, by Raymond Bird 
- The Prehistory of the 1900 Series Arthur Humphreys 
-  Wikipedia
- The Staffordshire University Computing Futures Museum Computers Page