The computer, which weighs 2.5 metric tons (2.8 short tons), was built and used at the Atomic Energy Research Establishment in Harwell, Berkshire. Construction started in 1949, and the machine became operational in April 1951. It was handed over to the computing group in May 1952 and remained in use until 1957.

It used 828 dekatrons for volatile memory, similar to RAM in a modern computer, and paper tape for input and program storage. A total of 480 relays were used for sequence control and 199 valves (electronic vacuum tube) for calculations. The computer stands 2 meters high, 6 meters wide, and 1 meter deep with a power consumption of 1.5 kW. Output was to either a Creed teleprinter or to a paper tape punch. The machine was decimal and initially had twenty eight-digit dekatron registers for internal storage, which was increased to 40 which appeared to be enough for nearly all calculations. It was assembled from components more commonly found in a British telephone exchange.