I was changing a damaged socket face in my lounge this weekend past. I had turned the downstairs ring main MCB off yet still had power to the socket. All the other sockets on the downstairs ring were off. I then turned the upstairs ring MCB off as well. This shut off power to the socket, so I thought that this individual downstairs socket had been wired as part of the upstairs ring. However when I turned the downstairs MCB back on , power returned to the socket. In essence this socket appears to be on both ring circuits, upstairs and down. There are only two cables coming in/going out of the socket. How can it be?