Photos: National Museum of Computing highlights

The biggest draw for most visitors is the room which houses the Colossus. This beast of a machine is considered by many to be the first of the electronic digital machines with programmability. There were others before it, but this was the first to be digital, programmable and electronic.

The machine on display is a rebuild of one of the original machines sited at Bletchley, and took over 10 years and around 6,000 man hours to finish. The computer was used to break Nazi codes during World War 2, and was so secret that it was not included in the history of computing for many decades after the end of the conflict.

The whole project was put together using just eight wartime photographs taken in 1945, a few fragments of circuit diagrams which had been sneakily lifted by the original project engineers despite the massive secrecy, and the help and advice of Henry Fensom, one of the men who built the computer first time around.

Next up on the tour was by far the largest system on display, an ICL 2966 from the early 1980s, which looks all the world like a launderette full of top-loading washing machines. Donated to the museum by Tarmac some 15 years ago, the system remained in storage until early 2008 when space was found to display around 40 per cent of the original components. Anyone familiar with the inner workings of a modern hard drive will recognise the historical importance of this system as its storage relies on a series of large layered disks with servo-powered read/write heads. The disk sets are removable and are stored in transparent plastic containers.

The surface of the disks is incredibly fragile and can be problematic, according to one of the facility's directors, Andy Clark. "These systems would have originally been housed in totally clean, dust-free environments, much the same as hard drive manufacturing facilities today. We have to be really careful about handling the disks, and eventually hope to house the exhibit in a clean room," he told us.

The Elliott 803B is missing one of its data storage units, which uses traditional 35mm film coated with a magnetic emulsion made by Kodak, but it is still capable of burbling away to itself playing what we were reliably informed was music. Work continues on the system today and, if anyone has the second tape unit gathering dust in a store cupboard somewhere, we're sure the folks at Bletchley would be delighted to hear from you.

Caked in the grime of decades, and smelling faintly of overheated copper wiring, the Harwell waits patiently for the museum's eager volunteers. "It's been in storage since the 1970s, and it will probably take us more than a year to make sense of it, but we'll get there in the end," enthuses Peter Onion.

Although the museum's main focus is on the pioneering computers which started the whole digital ball rolling, one recently opened addition to the many exhibits is the Personal Computing Gallery. It's a bit flasher than some of the other areas, and makes an effort to be a bit swish and interactive without going too far. Everything from the Sinclair ZX81 through the BBC Micro, past the Amiga and on to modern Macs and PCs is represented, and there is even a display charting the history of hand-held computing.