From wikipedia:

“At 377 metres (1,237 ft) above sea level it is the highest lake in England”

I’ve seen this claim in a number of places. The National Trust site says: “Malham Tarn is the highest upland lake in England” . But surely there are several higher lakes in the lake district?

For example, also from wikipedia:
“Red Tarn is a small lake in the eastern region of the English Lake District, in the county of Cumbria. It is high up on the eastern flank of Helvellyn, beneath Striding Edge and Catstye Cam.
It lies at an altitude of 718 metres (2,356 feet)”.

Is it based on overall size?

What’s a lake? Is there a size limit? All a bit arbitrary I would have thought. I camped at the (allegedly) highest lake in Wales just below the summit of Carnedd Llewelyn. No doubt someone can find a higher pool somewhere.

Well, red tarn is about 400m end to end, so it’s not exactly a garden pond.
Maybe there is a official size limit for a lake?

I can’t understand that unless it’s meant to be highest of its size.

I found this too:

“Hayeswater is a small lake within the Lake District of Cumbria, England.

The lake is situated about a mile (1.6 km) SE of the hamlet of Hartsop in the Patterdale Valley. It nestles between The Knott to its west and Gray Crag to the east and it is at an altitude of almost 1,400 feet (425 m).”

Plenty of glacially formed tarns in the lakes will be higher as you say.