Reminiscences of BTM and the CANTAB Machines (Bombes)

Engineers' Department: of BTM in peacetime would have been the design department for Tabulators and the punched card equipment made by BTM in its Letchworth Factory, but during the 39-45 war time it was given over entirely to the development, assembly and testing of the CANTAB code breaking machines. These were nothing to do with the normal punched card business of BTM as such, but were conceived by mathematicians from Cambridge University working on code breaking methods, and engineered by BTM using similar electro-mechanical techniques to those used on punched card equipment. (The main BTM products continued to be made in the rest of the factory, and were, of course, used very widely by Government Departments and the Forces.) The Code Breakers using CANTAB machines called them BOMBES after the name given by the original code breakers in Poland prior to the war.

The Department was located in the South West corner of No.1 Factory in Icknield Way at the junction with Cromwell Road. It consisted of a Drawing Office located at the front of the building upstairs, the Test Room at the side nearest to Cromwell Road with the Workshop adjacent comprising a machine tool area, fitting benches and an assembly area for the Bombes. The Wiring Girls were on the floor above the Test Room, which was reached by stairs in the workshop area.

This part of the factory had its own entrance, but otherwise there was surprisingly little security at the time, which would have appalled present day experts, especially when Churchill considered the intelligence derived from the system to be his ‘most secret weapon' or his ‘golden eggs.' A wire cage surrounded the department in the factory, staff had passes, but there was never any need to show or wear them, although I think we did eventually have a civilian security man. Moreover, the finished machines were sometimes dispatched in an open back lorry and just covered with tarpaulin. In the absence of a security guard, for the first half hour of my day, it was my job to man the front entrance door between 7.30am, when the floor started and 8.00am, when the Wiring Girls came in, and then to lock up. I learnt how to hold back the clocking in machine from changing from blue to red ink – signifying lateness, which was helpful to one or two latecomers!

A brick room was built on the corner of the roof to accommodate the Fire Watchers. There was a rota for the staff to do these night duties, with no time allowed off during the day.

D-Day: I well remember at 7.30 on the morning of D-Day, 6 June 1944, sitting on the steps of our entrance to the factory, watching the constant stream of aircraft towing gliders on their way to Normandy, an amazing and memorable sight! It was a beautiful sunny morning with white fluffy clouds and the sky seemed full of these planes with their distinctive white and black stripes on the fuselage and wings.

People at BTM: The Chief Engineer in the Engineers Department was ‘Doc' Keen, a hard working but rather remote and unapproachable character. To me he seemed to be always wearing the same brown suit and smoking the same curly pipe! He was also the organist and choirmaster at St Michael's Church which stood in Norton Way South opposite the paddling pool where there is now an office block. He would tend to recruit his apprentices from among his choirboys – Albert Butt and Eric Palmer being my contemporaries – but not me!

Our Foreman was Gerry Simister who wore a white coat and seemingly stood for hours in his office gazing at us workers. Someone unkindly nicknamed him ‘Fish Eyes'! Alf Archer was the charge hand and wore a brown coat with red collar and cuffs. He was a more kindly person and would give youngsters fatherly advice. George Bonfield was the shop floor supervisor and deputy charge hand. He was likeable, quietly spoken and very helpful to us. (Incidentally, his son is the present ICL Chairman and Chief Executive.) ‘Jock' Darge was the Supervisor of the Wiring Girls. He was a ‘wee' Scotsman as might be imagined, who had a dark Hitler-like moustache!

Other names which come to mind are: - Vic Sothcott, Fred Sinfield, George Chance, John Smith, Bill Borght (fitters); Wally Gaunt, Adrian Routledge, Ron Grimes, Denis Whelan (Test Room); Jack Rutter, Roy ‘Woggie' Davis (Turners); Bill Vines (Shop Steward), and Ted Spinks (Miller), Eileen Whelan, Beryl (Wiring Girls).

Because of the necessity of reaching the required production level, many of the Fitters and Test Room Engineers were conscripted from elsewhere in the Country, such as Instrument Companies and the Post Office Engineering. They had the benefit of being in a reserved occupation. They were lodged in private houses in the town and around the locality.

I also remember there was a civilian named Skeen (e) who would turn up from time to time on a motorbike and sidecar. He invariably had a Wren with him in the sidecar. I believe he was a liaison officer, probably from the War Department, to co-ordinate manufacturing activities and deliveries of machines to either Bletchley Park, Stanmore, or Eastcote.

Work on the Bombes: I joined the ‘Engineers Department' at No 1 Factory in Icknield Way, Letchworth, at the age of 16 in August 1943 straight from school, as an Apprentice Precision Fitter. There was then no specific apprenticeship scheme – you just worked with the skilled men on the various machines (lathes, millers, shaper, drills, grinders etc.) and bench work using hand tools. I remember we had one curious but remarkable flexible machine called “The Triplex” which could be used as a lathe, miller both horizontal and vertical – and drill, the headstock being moveable upwards on a quadrant arm. The bed could be angled and raised or lowered.

My first task at BTM was to work with a Fitter who was Australian. I can only remember that he was nicknamed ‘Digger' inevitably. Our job on the Bombe was to line up the bearing plates for the drum shafts and then dowel pin them to the angle-iron frame. (The frames were manufactured elsewhere in Letchworth.) There was a special technique for this. These drum shafts were driven through gear wheels meshing with worm gearing on long horizontal and vertical drive shafts. These in turn were driven through a gearbox, which was itself driven from a large electric motor housed in the bottom of the machine. There was a vast array of brass piping fitted to bring oil to the drum shaft bearings, which were plain bushes, and the shafts had spiral oil grooves. I think this system was fed by a hand-operated oil pump.

Obviously an oil tray was needed at the base of the machine. When all the mechanics had been fitted, the machine was wheeled into the Test Room to have its electrical components and cabling fitted. Much of this was on a large hinged door-like angle iron frame carrying rows of trays containing high-speed relays called MSM's. I think this was mainly done by some of the Wiring Girls. It would then be tested by Engineers. When up and running, it would emit a great whirring sound, something like a couple of dozen washing machines! Finally, the machine was fitted with sheet metal covers leaving only the drum shafts visible.

For a time, later on, I was moved to a room at the back of what was then the Fusarc factory (they made welding rods) further down Icknield Way, almost opposite to Irvins, with Albert Butt, Eric Palmer and three of the Wiring Girls. Our job was to assemble and test a separate unit made of an angle iron frame which was about 3 feet wide and deep, 5 feet high with a sloping front, to which were fitted three rails of connectors with the associated cabling. I believe they were connected to the Bombes by a standard Hollerith ‘Quick Link' cable and provided cross plugging facilities to enlarge the range of decoding. We were provided with an automatic test set incorporating a uni-selector, which detected short and open circuits.

After this, I returned to the Department in No 1 Factory and worked on the fitting bench, making brass bars on which to mount solenoids with plungers, which were fitted to the keys of Remington Electromatic Typewriters imported from USA, so that they could be electrically operated from the Bombe.

The Wiring Girls made cable forms for the inter-connection wiring on the Bombes, and also assembled the decoding drum. Cabling was formed by running wires along a route of nails used as posts on a large wooden board, and then terminated by brass plugs or spade clips soldered at the ends. The girls assembling drums would sit at rows of benches with individual lamps because of the fine work involved.

One of the jobs given to us apprentices was to make the special tools used by the girls assembling the drums, such as miniature screwdrivers, plug insertion tools, and a tool for adjusting (‘tweaking') the wire commutator brushes.

Most Fitters had their own tool chest, and I still have mine with some of the tools used in those days. It is a Neslein, purchased from Brookers in 1943.

Worker comforts: I remember that at about 9.00–9.30am a trolley would come round with tea, coffee, hot chocolate, and rolls with sausages. From 10.30–11.00am and 3.00–3.30pm. Music While You Work would be broadcast over the factory Tannoy, then at 5.00–5.30pm music from BTM's own records would be played.

Food parcels: BTM then had a business relationship with IBM in the United States. We were therefore privileged to periodically receive the very welcome food parcels, which came over from IBM. We then thought that Spam and Tex lard were luxuries!

Air Raids: As far as I know, the Germans had no knowledge of the BOMBES or where they were made. The nearest we got to being bombed was when a long range petrol tank fell off an American Lockheed Lighting fighter plane fell into Cromwell Road some 20 feet from the factory where we were working.

Stephen Hare
January 1996

These notes were in a folder in The First Garden City Museum I had requested I have a copy for background information only. I then made contact at the last know address of  Stephen Hare but sadly he had passed away some months after writing this article to paper. Mrs Hare kindly gave me permission to use the article in full.