History tells us that many of the major milestones in the development of technology throughout the 20th century happened in garden sheds and garages.

Henry Ford built his first car, the Quadricycle, in a converted storage shed in the back yard of his Detroit home. Steve Jobs and Steve Wozniak put together the first Apple computer in the garage of Jobs's family home in California. And Nigel Xerox invented the graphical user interface in his grandmother's coal bunker. OK, we made that last one up. But you get the idea.

All of which makes it quite fitting that the National Museum of Computing is based in what is ostensibly a very large garden shed nestled in the grounds of the wartime code breaking headquarters at Bletchley Park.

The museum, which is home to many of the most important and pioneering computers ever built, is run by as enthusiastic a band of volunteers and trustees as you will find anywhere. Every one of them has a singular passion for the history of computing, and that passion is surprisingly infectious.

One of the facility's directors, Andy Clark, points out the ethos behind the exhibitions. "It's a museum of computing, not a museum of computers. It's not about looking at the boxes, it's about what the boxes can do. Every exhibit is fully operational and capable of doing the job for which it was designed," he said.

It's this ethos which keeps the volunteers extremely busy, repairing hardware, obtaining hard-to-find components from the most unlikely of sources, and rebuilding incredibly important historical computers from seemingly random boxes of un-catalogued bits and pieces in some cases. What would seem a daunting, if not impossible, task to many mere mortals is what keeps this band of beard-scratching boffins smiling.

They don't come much more beardy than Peter Onion, with his shock of long blonde hair and ZZ Top facial fuzz. Onion showed us his latest baby, an (almost) fully functioning Elliott 803B, with such pride that it is quite touching. The machine was found rusting in a breaker's yard around 15 years ago, and has been restored to such a high level that it could have been recently installed.

It 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.

By far the largest system on display, an ICL 2966 from the early 1980s, looks to 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 Clark. "These systems would have originally been housed in totally clean, dust-free environments, much the same as hard drive manufacturing facilities today," he told us. "We have to be really careful about handling the disks and eventually hope to house the exhibit in a clean room."