The National Museum of Computing

The National Museum of Computing: Where the Machines Still Breathe

Step through the doors of Block H at Bletchley Park and the first thing you notice is the sound. Not silence — not the reverent hush of a conventional museum — but the hum and click of valves warming, relays tripping, and paper tape threading through readers that last operated in anger when the world was at war. The National Museum of Computing is not a place where history sits behind glass. Here, history runs.

A Building Worth Fighting For

The story begins not with a grand opening, but with a rescue. By the early 1990s, the Bletchley Park estate — where codebreakers had shortened the Second World War by an estimated two years — faced demolition and redevelopment. The Bletchley Park Trust, established in 1992, saved the wider site. But Block H, the low, utilitarian building where six of the original ten Colossus computers had once cracked Hitler's most secret communications, needed its own champions.

That champion was Tony Sale. A scientist, former MI5 officer, and the first curator of the Bletchley Park Museum, Sale possessed a rare combination of deep electronics expertise and stubborn conviction. In 1993, working from scraps of diagrams, faded photographs, and the half-forgotten memories of wartime engineers, he and a band of volunteers began the extraordinary task of rebuilding a Colossus Mark II — the world's first large-scale electronic programmable computer — in the very room where it had originally stood.

By 1996, a working prototype was switched on by HRH The Duke of Kent, in the presence of Tommy Flowers himself, the Post Office engineer who had designed and built the wartime originals. When Block H faced demolition again in 2004, Sale secured Grade II listed status for the building. The Codes and Ciphers Heritage Trust was formed in 2005, and by 2007 it had evolved into The National Museum of Computing — an independent charity with its own entrance, its own mission, and the world's largest collection of working historic computers.

Eighty Years of Computing, Alive Under One Roof

What makes TNMOC extraordinary — and what earned it recognition as one of England's top 100 "irreplaceable places" — is the sheer span of working technology under one roof. The museum's motto is Conserve, Engage, Educate, and Inspire, and it delivers on every count.

The journey begins in the 1940s with the rebuilt Colossus itself: five tonnes of metal and 2,420 glowing vacuum valves, occupying the exact spot where its wartime predecessor once stood. Nearby, a working reconstruction of the Turing-Welchman Bombe — the electromechanical device that cracked Enigma — clicks and whirrs through hourly demonstrations. A replica of the Heath Robinson machine and the British Tunny round out a wartime gallery that no other institution on earth can match.

Move forward a decade and you encounter the Harwell Dekatron computer, built in 1951 and later renamed WITCH — the Wolverhampton Instrument for Teaching Computation from Harwell. Found languishing in barn storage in 2009, it was painstakingly restored and now holds the Guinness World Record as the oldest original working digital computer. Its dekatron valves still pulse with a warm orange glow, counting in base ten with a patience no modern chip could match.

The Large Systems Gallery tells the story of mainframe Britain. A Marconi TAC that monitored the Wylfa nuclear power station from 1968 to 2004. An Elliott 803 rescued from fifteen years in a farm outbuilding. An ICL 2966 mainframe so vast it occupies a third of the gallery floor. A PDP-11 that once supported Dungeness B Nuclear Power Station. These are not replicas or cases of circuit boards — they are the actual machines, restored and running.

Then comes the era most visitors remember personally: the personal computer revolution. A gallery packed with Sinclair Spectrums, Commodore 64s, early Apples, Amstrads, and a NeXTcube similar to the one on which Tim Berners-Lee developed the World Wide Web. A classroom of working BBC Micros — part of the 1.5 million units that introduced a generation of British schoolchildren to programming — invites visitors to type, load, and run just as they did in the 1980s.

Independence and Survival

TNMOC receives no public funding. It operates as an independent registered charity, sustained by ticket sales, corporate supporters including Fujitsu, Google, IBM, and HP Labs, and the generosity of individual donors. Its volunteers — many of them retired engineers who built or maintained the very machines on display — are the museum's lifeblood, keeping decades-old hardware not merely presentable but operational. The museum also runs an ambitious education programme, offering learning visits and bursaries to bring school groups face-to-face with the physical reality of computing's past.

Tony Sale, who drove the museum into existence through sheer force of will, died in 2011. But the institution he built has only grown stronger. A team is currently constructing a working replica of EDSAC — the Cambridge computer whose calculations contributed to three Nobel Prizes. The 2024 restoration grant will preserve Block H's original wartime structure for decades to come. And in 2024, full national accreditation confirmed what visitors have known for years: this is a museum of genuine national importance.

Visiting

The National Museum of Computing is located at Bletchley Park, Milton Keynes, Buckinghamshire, a short walk from Bletchley railway station. It operates its own entrance, separate from the Bletchley Park Trust. The museum typically opens Tuesdays, Thursdays, Saturdays, and Sundays, with hourly demonstrations in the Colossus, Bombe, and Tunny galleries. Guided tours run at 2pm on select days — booking is recommended. Visitors can also explore the collection through a 3D virtual tour online.

This article was partly inspired by a collection of old photographs and home recordings that came to light when someone brought their personal memories to be digitised. Amongst the reels and prints were images connected to Bletchley Park's post-war years — and it made us wonder what else might be out there, tucked into attics, shoeboxes, and old cupboards, with connections to The National Museum of Computing and the people who built, operated, or preserved these remarkable machines. If anyone holds old media connected to this organisation, services like EachMoment can help preserve them for future generations.