Well I have a PhD in physics and I operated lots of high voltage instruments and I can tell you that you'll need about 30,000 volts assuming dry air and 30kv sparks will generate (soft) X-rays and take out your mains earth leakage circuit breaker unless you hold it closed by placing strong tape on it to prevent it closing.
Also be sure to unplug all your ESD sensitive equipment ie computers, TV's etc and you should probably ask your neighbours to do the same.
I miss those days.....
