Ninis was educated at Lincoln School and Durham University. He was ordained deacon in 1930; and priest in 1931. After a curacy at St Stephen, Grimsby he was an SPG Missionary in India from 1932 to 1934;and with the Indian Ecclesiastical Establishment from 1935 to 1941. He was a Chaplain to the British Armed Forces from 1941 to 1947. In 1948 he became Vicar of Figheldean; and in 1953 of Market Drayton. he was also an Honorary Chaplain to the Queen from 1965 to 1976.