Acorn Archimedes A3000
This is the second machine of the Archimedes line-up, it's the first computer with an ARM-processor, which are still actual in modern mobile telephones.
This is the first all-in-one, that only lacks a monitor, the keyboard, mainboard and storage for data, are build-in. Hence the name AiO.
The A300 is the last of Acorn machines that has the BBC-label as name. It's running on Risc OS2.