At this time of year there are always wasps visiting the pond to drink but yesterday was the first time I had noticed this particular variety. A Median Wasp - Dolichovespula media. Common to much of Europe this is a relatively new species to Britain having appeared in the 1980s
Not the best of views but it wouldn't cooperate, always coming back to the same lily leaf and always facing the same way. For a good view showing the markings and shape hover over the thumbnail on this page on Garden Safari.