Postcard from ... Bletchley Park

Visitors arriving by train in Bletchley, 40 minutes northwest of central London, may notice that the station name has been joined by signs proclaiming it the “home of the codebreakers”.

Even now, it’s a shock to see the past of this Buckinghamshire town so brazenly presented. As recently as the early 1990s, the existence of Bletchley Park, Britain’s second world war intelligence hub and the place where the Nazis’ Enigma codes were first broken in 1940, was still a half-forgotten half-secret.

In 1992, the Bletchley Park Trust was set up to save the site from being sold off for development. It opened as a museum in 1994, and 10 people turned up for the first tour. Now, after an £8m lottery-funded grant, Bletchley Park has been transformed into a major visitor attraction, with a long-term aim of attracting 250,000 people per year to see its extraordinarily vivid recreation of the spartan working conditions of the wartime codebreakers.

The importance of the place was summed up in July 1945 by Dwight D Eisenhower, then supreme commander of the Allied forces, when he wrote to the head of British intelligence, saying: “The intelligence from you [Bletchley Park] . . . has been of priceless value. It has saved thousands of British and American lives.” It is also estimated to have shortened the war by up to two years.

Much of the intelligence to which Eisenhower referred was generated in temporary huts in the grounds of Bletchley Park, a country house that had been bought (with some foresight) as an out-of-London base by British intelligence in 1936. The lottery grant has financed the overhaul of Huts 3 and 6, which have been restored to their wartime appearance, with bomb-blast walls, a muted green-and-beige colour scheme and bare floorboards. Conditions in the huts are just as they would have been in the 1940s – stifling in summer and freezing in winter. There are coats and hats hanging on pegs, full ashtrays, paperwork and cups of tea on the desks. Walking around the offices listening to the sounds and voices of the period is evocative enough; knowing that the people who worked here – three-quarters of them women – had to keep extraordinary secrets, even from co-workers, makes their achievements even more astonishing.

Another part of the development, a reception and visitor centre, gives context to the code-breaking and intelligence work. There’s also a new exhibition about cybersecurity and online safety, funded by McAfee, the computer security company. It doesn’t feel too incongruous, given that the first electronic computer was developed here as part of wartime work and it gives modern twist to now-distant wartime work. After the quiet focus of the huts, however, the neon colours and flashing panels in the cyber exhibition are jarring, and walking through feels rather like being in a scene from the Disney film Tron.

At the height of the war effort, from early 1943 onwards, Bletchley Park codebreakers and signals intelligence staff were processing 10,000 incoming messages a day, from every war zone, sending coded messages to British forces and agents, as well as running a whole network of fictitious agents and sending false codes in order to misdirect the enemy. There were up to 9,000 people on site and 1,500 local support staff.

Many of the people who worked here went back to civilian life without ever mentioning their wartime efforts. In Bletchley Park mansion, a display book lists their names. Its pages are turned every day – on my visit, I notice a name that matches that of an elderly teacher from my primary school days. Was it her? Did she work here? I’m intrigued.

At a reception to mark the opening of the new visitor centre, I am introduced to Betty Webb. From 1941 to 1945 she worked in Block F, now demolished, home to the Japanese section. Her job was to paraphrase decoded and translated messages, which were then sent on – coded so that they would not be recognised as having been intercepted – to British forces and agents.

What, I ask, does she think of the reborn Bletchley Park? “It feels marvellous, just as it was, especially the new tennis courts.” The landscaping around the mansion has been restored to look exactly as it was in the 1940s – the space where Betty and her colleagues enjoyed fresh air, games and a break from the struggle to win a global war. It’s a sobering thing to contemplate over a picnic lunch.

Isabel Berwick was a guest of McAfee and Bletchley Park Trust (bletchleypark.org.uk). Entrance to the museum costs £15 for adults, free for children under 12

Photograph: Shaun Armstrong