According to the Rogerster Ferranti Argus 500 was being used by the army to design surface-to-air missiles they used "big old Winchester-style disk machines which looked like spin dryers and took platter disk packs, one active and one backup."

Argus and its disks lived in their own air-conditioned cool clean room and a phone line to tech support in the days when most homes didn't have a phone. 

One night the machine had crashed and produced a burning smell. A dead disk was found and opened and particles of polystyrene insulation all over the disk pack."

It looked like a mouse that had burrowed into the disk cabinet and scattered material onto the disk and gnawed its way into it. While the mouse had gone tech support wondered how it had gotten into the sealed room.

It turned out that the night shift was given boxes of rations and thought that air conditioned data centre was better than sweating it out in the summer.  So they were popping in there to eat and stored their food in the computer room, in lieu of a fridge.

Mice followed, which is odd really because the Ferranti was a primitive, pre-GUI machine.