REDD was the Recording Engineering Development Department at EMI in London. Most Beatles recordings were made using a custom-built REDD.51 mixing console. Their first 4-track console was a REDD.31. Much later, after Magic Alex — the self-proclaimed genius of Apple Electronics — was revealed to be a fraud, the Beatles borrowed a couple of REDD.31’s to begin recording “Let it Be.”
Here’s some history of what happened to one of the consoles, starting ten years after the Beatles were done with it.