Just to add my bit to this, I agree with DS, looks like the 3rd photo (master socket with orange and white) is the 2nd line.
My other concern as previously mentioned is the green/black connected on the front plate, this would be an external extension bell by the way it is connected.
Maybe time to disconnect wires and/or disconnect any extension socket that is no longer required, looks to be an historical fault at some point due to the use of orange wires for the line rather than blue.
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