Hoverflies are perfectly harmless insects that often get swiped away and swatted because they look like bees or wasps and people are afraid they or their children will be stung. Nothing could be further from the truth. Yes they do resemble wasps, but this is an evolutionary ploy to prevent predators from eating them.
As a group of insects they are delightful to study and get familiar with. So next time you see a 'wasp' take time to take a closer look before you swat it away, take a picture if you can and look on the internet and you might be surprised to learn what it really is and who knows it could be one of the rareties.
These two are readily found locally, Eristalis pertinax and the Marmalade fly.
The North Kent Marshes are a very special area and worth preserving at all cost.