Having studied law before attempting to enter the civil service, Coutanche entered the chambers of John Beaumont at the
Middle Temple in 1912. He aimed to practise at the Chancery bar, but was instead called to the Jersey bar in 1913. Upon the outbreak of the First World War in 1914, Coutanche served as an assistant to a government secretary in Jersey. He was ineligible to join the Inns of Court regiment due to his previously discovered heart murmur. Therefore, he went to work at a munitions factory, rising from a worker through to management level. He was called to the English bar in 1915. In 1917, he volunteered for work with the War Claims Commission and was posted to
Belgium with the rank of lieutenant. During his time in Belgium, he won the Belgian
Croix de Guerre and was appointed chevalier of the
Order of the Crown (Belgium). He left the army in 1920 with the rank of captain. He returned to his chambers in
London, but then had to return to work at the Jersey chambers due to the illness of his father. He was elected a Deputy of Saint Helier in 1922, and married Ruth Sophia Joan Gore in 1924. ==Attorney-General and Bailiff of Jersey==