Black Darter?

After a dismal start the day brightened so JK and I made the most of a window of opportunity this afternoon and wandered up to the Dragonfly Lochan. We were rewarded by not only the autumnal tranquility of the Lochan but by seeing two dragonflies, which we think were late flying Black Darters. After short flights amongst the mares' tails one of them obligingly settled on the wooden railing and basked in the sunshine. (See extra). Can anyone confirm our identification?