Mayfly for ID, please

Mayfly for ID, please

Observation - Mayfly for ID, please - UK and Ireland. Description: I've been puzzling over these for a long time. Found in grassland and inside an isolated building adjacent to a freshwater loch. They look like one of the three-tailed mayfly species but the dark brown body with narrow yellow stripes and the dark tip to t

I've been puzzling over these for a long time. Found in grassland and inside an isolated building adjacent to a freshwater loch. They look like one of the three-tailed mayfly species but the dark brown body with narrow yellow stripes and the dark tip to the leading edge of the wing doesn't in any of the books I have or websites I normally frequent.
With some hesitation I'm going to suggest that it's a non-UK species, the Black Quill (Leptophlebia cupida).