On 2020-08-02, Martin Brown wrote:

Simplest way to get an ID is take a couple of representative fruit plus
a picture of the flowers and general shape of the tree along to a local
apple day in the Autumn. Unfortunately there may not be any this year

Make that a few more, about 4-6 specimens if possible. Apples of one
variety can be quite variable - especially colouring depending on whether
they have been in shade or bright sun.

National Trust and English Heritage places often have such events with a
wide range of unusual locally grown apples on display and an expert on
hand at the weekends. Sometimes they get lucky and see a novel variety.

Experts visited a newly renovated walled garden near me to get samples
of rare old pear trees not previously known in cultivation.

I live in Cornwall. Would there have been a particular variety here?

A lot would have been cider apples.