I consider this one one my best - taken 'under the lights' - long after non-flash photography was possible.
Taken using 2 580EX flashes, mounted 1ft off of the ground and attached to the leg of the monopod supporting the 400mm.
Flashes tripped using a ST-E2 remote pointing down at the flashes attached with a remote cord.
Was quite the get-up! But worked perfectly.