The sparks who wired our kitchen extension and put in a new consumer unit says we have 2 radial circuits downstairs - 1 for the lounge & kitchen; 1 for the 'study' which he connected to 2 MCBs in the unit. I now wish to extend the 'study' circuit out into our newly finished conservatory. When I tried to isolate the circuit today I had to switch off BOTH MCBs at the unit (each one on its own had no effect) and, of course, both circuits went off. When I switched ONE back on, both circuits came back on! I don't understand!