A Hovering Whopper!

I think this must be the largest hover fly I've ever seen. I thought it was a hornet at first. Sadly, I've not seen a single one this summer.

After consulting my well worn copy of Collins Complete British Insects, I think it is the hornet hover fly. Hence my first thought. 

It's not all that common to see them this far north, so I was quite chuffed to spot it.