Very many thanks Roy Kelly for finding this bird and promulgating it on Twitter on the morning of 24th which enabled all the people in this thread to see the bird, including me.
And again at 17.30 on red bouy at dam end ,nice close views
Juv` Black Tern still present 1430 h`rs 25/08/2017
24-Aug-2017
Juv Black Tern at Durleigh Reservoir today, it was still present when I left there at 15:00 hrs.