Green Drake or Common Mayfly

This little Mayfly had landed on my arm as I walked back indoors after sitting down on the river bank.   I gently moved it and fortunately it landed on the inside frame of the patio door where I was able to photograph it.   I hope I'm correct in my identification. 
The body was about a 2cms long with three tails that were in excess of 5cm and two antennae about 3cms in length, and the most beautiful veined wings and chevrons along the body.     Apparently they are in decline so it was good to see and study one so closely.
He flew back outside where I hope he wasn't an easy lunch for a bird.