Just putting in a fused spur off the ring main - only 6 inches away from
existing double socket
Carefully removed plaster next to double socket - all clear.
Marked the position of new backbox for fused switch.
Drilled a honeycomb of holes where back box to go.
When I started chipping plaster out - I found that a diagonal 6mm cable for the
cooker ran straight through where the box was to go.
I had actually drilled through the T&E - a perfect hole straight through - it
had not tripped RCD or fuse.

Question: The cooker was recently wired in as part of a kitchen upgrade : are
diagonal runs permitted under the relevant regs?