Leonard Horatio Slatter was born in Durban in 1894 and educated at Selborne College in East London, where he excelled in mathematics and science. Upon completion of his studies, he went to Battersea Polytechnic in London, England to train as a civil engineer. At the outbreak of the First World War, he joined the Royal Navy.
Later, he was transferred to the Observer Section, which was at the time trying to design an aerial navigation system.
Slatter was next posted to the Seaplane Squadron based across the English Channel at Dunkirk
