The electrical supply from the house has to come a long way: from the fusebox, up under the floor of our bedroom, out the wall and through a 18 inch deep trench under the patio - which is part concrete. I had a very hard time chopping through the concrete (especially the part where I found a metal plate reinforcing the slab - I decided in the end not to cut through this but to burrow underneath it) but for most of the trench all I had to do was lift paving slabs and dig a lot:
I'd prepared the way through the house for both the electrical supply and the network cables I needed to run, so when the electrician came he had a reasonably simple job to do and finished in a single day, laying steel wire armoured cable outside and fitting a new fuse box, sockets and a light to the new office:
The spare cables you can see are 3 CAT5 network cables which are also buried in the trench - although protected in 32mm waste pipe here, and in conduit when on the walls. They run from the front hall and will carry network traffic, a phone extension and possibly an intercom (this only takes up about one and a half cables, so I have some spare wires!). I've also pulled through some orange builder's string just in case I need to put more cables in there in the future (I really don't want to dig it all up again):
The power supply all works and I've started filling in the trench: the network cables have been fitted to a proper faceplate and box to keep things tidy: here's me testing the network connection:
So now all I need to do before I move in is to finish the panelling, paint if I think it's necessary, add some shelves and a carpet - shouldn't be long now.