Possible lightning step leader

This image has been bugging me for years, i was filming a storm in July 2009. The storm was pretty much overhead with sporadic lightning, i still cant decide if this is a genuine step leader or just an image ghost. It appears on a single frame, followed by near instant thunder. All the strikes i filmed that day where a much brighter blue as apposed to this purple one which is odd. Also under it is a tall metal umbrella stand in my garden...