I think it was summer 1994, starting around late July time, there was a two week period up in County Durham where we had quite severe thunderstorms nearly everyday; it was tropical weather of warm humid days and an afternoon thunderstorm. I vividly remember clear blue skies and I heard thunder, the storm was still quite a few miles away (I am guessing the thunder came from a positive flash).
Never seen anything like that setup since. I think 1996 was another year when I experience one of the longest thunderstorms, it started around 4pm and continued on right through the night and was still going in the early hours.