This isn't actually taken at the RNCM. It was taken in the Ruhleben camp for English prisoners of war in Germany, 1916.
The story is that Carl Fuchs, a 'cello professor at the Royal Manchester College of Music (1893-1973) visited his mother in Germany in the summer of 1916. When WW1 broke out he was detained in the camp since he had a British passport.
However, since he had completed his national service in Germany in his youth, he was released after a handful of months and was able to continue his performing career but only in Germany.
Whilst he was in the camp, however, he worked together with a few fellow prisoners and founded an orchestra (as you do). This photograph was taken of the orchestra after Fuchs has left the camp and sent to him as a greeting card.