Ragnar,
That has to be the simplest Temporary I've seen in a while.
I once saw an Electrician cut the plug off of his extension cord, strip back the wires, attach the Earth and Neutral wires to the appropriate bars in the switchboard.
The seal was then broken and the phase wire shoved into the Line terminal of the Main meter.
He got some free power, until an Inspector dropped by to see what sort of metering equipment was needed for the building upgrade we were doing.
Oops!.