Morris started his career at an early age. He was 11 years old when one of his photographs was printed on the front page of the Daily Mirror. A camera fanatic since the age of 8, Dennis was known around his East End neighbourhood as Mad Dennis, due to his preference for photography over football. After inadvertently stumbling across a particularly feisty demonstration by the PLO one Sunday, the sharp young Dennis took his film to a photo agency on Fleet Street who promptly sold it to the Daily Mirror for £16. Accustomed to raising money for films and camera parts by taking photos of christenings and birthday parties, Dennis was suddenly on to something, his hobby and all-consuming passion could be done for a living.