Caning at Cothill4

There are apparently visible 2 large semi-circular darkened patches each about 9″in diameter on the lower half of each buttock cheek!This looks very much like the result of a severe and prolonged beating.However on the other hand it may just be mud from the adjoining bank-but as the subject is already in the middle of the water one would have thought that this would have washed off in the swim.As I say its impossible to tell due to lack of clarity.However perhaps in 1920 it was considered nothing strange to include such a photo?Perhaps serious students of CP would like to know about this and can help further on this historical point?Why is Cothill so important?Its probably the leading prep school in England though little heard of.the appendix states it has supplied pupils to all the major public schools including 448 to Eton and 156 to Harrow amongst many others!A long list of distinguished subscribers supported the school.