This thunderstorm was probably the largest and most powerful I have seen on the west coast of Scotland, it extended from here to Glasgow. We were at the North side of it, in dry conditions and most of the lightning was on the south side of Mull. The storm lasted a good 2 hours.
Lightning isn't easy to photograph, especially as the light levels were falling, in theory you just open the shutter until you see a good flash, in practice it is a lot harder, you are fighting the need for narrow aperture to reveal detail, and wide aperture to allow light through while at the same time trying not to over expose.
The twin strikes photo is stunning, and about as unique as you could get for Mull, as the Gribun Headland is so recognisable, and storms of this type so rare. I caught it by zooming in at the time there were concentrated strikes occuring in one area, and was rewarded by this image.
If you live where lightning is frequent, then I'd encourage you to try and capture it.