Alfred Cammeyer was officially one of the men cited as inventing the Zither Banjo and was for a while in partnership with Clifford Essex. After the partnership dissolved in 1900 he kept the workshop at 13 Greek Street, Soho, London for the manufacture of instruments, mainly Banjos but also some Banjoleles, under his name. 

The man in charge of the workshops was Sidney W. Young and he was responsible for most if not all of the later banjo developments from this workshop. When Cammeyer retired from business due to illness 1939, Young took over the workshop and continued to make instruments but under his own name and I don't know if Banjoleles were still being made at this point?