As most of you guessed the answer to the "Name that Bottom" Question is Sebastian, and the movie was Discipline Diary 1900
In which the unlucky lad gets figged, spanked and birched after a salt water sponging!!!
Those of you who suggested it was James Bruce were very close as he was in the same scenes and, as shown above they were dressed identically
I also wondered if some of you might think the bottom was the other end of this picture of James, whereas he is in fact being birched by Rich, rather than spanked by Rob
Thanks for all those who took part