No power when key in ignition

Any ideas what the problem could be.
The rear car is on axles stands, just putting new brake cables,shoes & cylinders on after  failing mot on the rear brakes.
I went to put  the interior light on and plug a torch in the cig lighter.
Nothing worked when i put the key in the ignition. No Immobilsor flashing no ign lights on dash lit up nothing at all.
It was all working sat when i put it away in the garage on sat am.
Paul

Car battery dead? Do you have a multimeter to test for 12v.
Battery cable come off?

Since both of those things are usually run off of direct power, that is you can turn them on without a key in the ignition.  I kind of agree that you may have a dead battery, and or a ground issue, however you may have blown a Fusible link from the Battery to the Fuse panel.

Check your fuses in the fuse panel, then look at a red accessory wire off the main power cable if it can  pull the wires and they stretch really really easily, then you have found your bad fusible link or links.  Disconnect the Ground prior to cutting out the old. The little wires not the one to the starter usually.

Yes you can spice a new section of fusible wire in to it, or replace the wire with new wire and a couple of fusible links.