Enigma (2001) is a better film. It, too, has a gratuitous spy plot. Actually, not only were there no leaks from Bletchley Park, the secret was kept until the early 1970s, and full details didn't come out until the 1990s. Turing was a reasonably important figure at Bletchley Park, which had about 9000 people at peak. But there were lots of other smart people working on the problem. Dilley Knox was in charge of the cryptanalysis, and Gordon Welchman did much of the design on the improvements to the Polish Bombe. Welchman went on to teach the first computer course at MIT and worked on computers until the early 1970s. He overcame his early opposition to vacuum tubes; he thought they would be too unreliable.

The real secret of US and British cryptanalytic efforts was to approach it as an industrial problem. That was new. Cryptanalysis until WWII was someone at a desk with pencil and paper. Cryptanalytic units were tens of people. The WWII effort on the Allied side involved not only Bletchly Park, but a big operation at Arlington Hall in the US and another operation in Hawaii. Bombes, the electromechanical key-testers, were built by the British Tabulating Machine Company, National Cash Register, and Western Electric. (NCR's was the most useful and was produced in large quantities.) About 60,000 people were involved at peak. It wasn't clear until long after WWII how big the operation was. Few people were allowed to see more than a small part of it. This wasn't a "one lone genius" thing.

Some of the secrecy was to make Churchill look good. There were times during WWII when Churchill sent a message to a general facing heavy opposition "Press on and you will be victorious", and took historical credit for his courage and decisiveness. Decades later we find out that Churchill had info such as "14th Panzer low on fuel and ammo, cannot fight for more than 2 hours" from intercepts. All German units sent in a strength return each day (all serious armies do this) which reads like "#1, 12000, #2, 450 ..." and is simply many effective soldiers, how much ammo, and other basic numbers. It's dull, boring, and tells which units can fight effectively and how far they can move. Much of Bletchley Park's work was decrypting and tabulating that info, which told Allied commanders where the weak spots were on the German side.