As a teenager, he lived in London, painting scenery in theatres; this was interrupted by the advent of the First World War, when he was arrested as an enemy alien and interned on the Isle of Man.
In 1921, he changed his name to John Decker and emigrated to America,[1]: 24 where he worked as a cartoonist for the New York Evening World until 1928,[1]: 31 when he moved to Hollywood and took up fine art.
One of his most famous portraits, depicting his friend and drinking companion W.C. Fields as Queen Victoria, hung for many years at Chasen's Restaurant in West Hollywood, California.
[2] Like his friends Fields and John Barrymore, the years of seemingly endless drinking sprees wreaked massive damage on his body, resulting in a premature death.
[4] Decker's father, Graf Ernst August von der Decken (1867–1934), grew up in the castle Ringelheim in Salzgitter, Germany, and became a reporter for British and German newspapers.