MRCS LSA 1865.
Fennell studied at St Bartholomew's Hospital. After qualifying Fennell was appointed physician's assistant and in 1866 junior house surgeon at MRI, a post from which he was dismissed in 1868. He then left Manchester and was resident medical officer at Leeds Public Dispensary before moving to Durham where he was surgeon to the Washington Colliery. By 1900 Fennell had returned to the North West and was medical officer for Tabley District, Bucklow Union. He was also a certifying factory surgeon and medical officer for HM Prison Knutsford. Fennell died, probably in the late 1920s, aged eighty four.