Occasionally I see comments in the forum suggesting that because some MOSFETs have a body diode between source and drain there is no need to put a diode across the inductive load they are driving. This schematic illustrates the situation, with the switch taking the place of the MOSFET and the 1N4004 taking the place of the body diode.
Here is the result of opening the switch, equivalent to turning off the MOSFET quickly.
Note
The trace is not exactly comparable with previous traces as I was not able to find the exact same inductor I used before, I just don't know for sure what I used, other than it was a winding of a mains transformer. However, the voltage spike clearly goes well below -200V.