DIY?

I've just been reading Paul Gannon's great book, Colossus: Bletchley Park's Greatest Secret, which is a readable and entertaining without deluging the reader in detail (whilst having the detail in the appendices). What I hadn't realised was how that Colossus was essentially a DIY project, that Bletchley Park engineers to some degree just didn't realise the strides that were about to be made. It reminds me of the data haven site in Cryptonomicon and the creation of the haven.