Phylum: Charophyta   Family: Closteriaceae

Closterium abruptum  W. West 1892

First described and illustrated by West (1892: 719, pl. 9: 1) from the Lake District, now Cumbria. It can be found with striae and, seemingly, without. Formae still exist that separate these taxa but, most likely, it's just a variable feature within the species. Similar to Closterium intermedium but that species is broader, almost without overlap.
Cell dimensions: L: 120-250 µm; B: 13-18.6 µm; Ap: 4.9-7.4 µm; L/B: 9-16.
A common acidophile found in peaty pools, often with Sphagnum, and vegetated loch margins.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M. (2024). Sieralgen in Drenthe.
West, W. (1892).. Algae of the English Lake District.