The unusual record was a mayfly called Ecdyonurus torrentis, this individual was trying to lay eggs on our wet patio (see photo BUT this is not the actual insect I saw, this one is a male of the species).
How it got to our garden I can only guess, the river is only about half a mile away as the mayfly flies but it is certainly not in line of sight and mayflies are not the strongest of flyers. Having said that who am I to try and second guess one the most successful types of flying insect that this planet has ever seen, having been around for over 300 million years. Bye for now, Lynn and Stuart