On Thursday I decided to go to see the adders after work as the weather had been bad all day but then the sun came out. When I arrived I saw that two, possibly three had paired up with a female. In the end I saw two definite adder couples, one single large female and two more single adders. One pair began copulating while I was there, so I took a few photos and then left them alone. In the third image you can see the tails locked and at that point I left. What a smashing evening!