We have three species of newts: Smooth, Great Crested and Palmate. These are the latter – the smallest British species, about 8-9 cm long. The newt at the back is a male – the spots and the red on his tail are part of his mating finery, and characteristic of male Palmate Newts.
…are both males. The webbed rear feet are also something males develop only during the mating season.
…this male has a thin filament at the end of his tail – another peculiarity of male Palmates during the breeding season.
My field guide says:
“Found in lakes, ponds and canals; often occurs in fairly acid pools on upland moors.”
Red Tarn fits the bill then.