Blue Tailed Damselflies 'in cop'

These Blue Tailed Damselflies were mating in the border of Grandma's pond this afternoon - 'in cop' as the naturalist would have it. Apparently during copulation the sperm of rival males is removed. This also occurs with the Dunnock, a mouselike bird of the hedgerow.
I used A Guide to the Dragonflies of Great Britain: Powell (ed Twist), Arlequin Press, 1999 to identify these damselflies and for further information.