Venerable Archdeacon Dr Devasahayam David Chelliah, popularly known as "DD", was born on March 14,1894 in Thirunelveli, South India. The fifth of nine children, he was the son of S. Devasahayam, a catechist, and Ponnamal, a teacher. 

He received his early education in a Tamil medium village school but attended an English medium Roman Catholic school in 1903 when he was nine. His father died in August 1907 when he was 13. Following his mother's footsteps, Chelliah became a teacher.

He moved to Penang in 1911 at the age of 17 when he accepted the invitation from Rev G.S. Price, principal of an Anglican high school, to become the headmaster of the primary school with a monthly salary of $40. In 1914, he joined the Anglo-Chinese School, Penang and was later appointed headmaster in 1935 during which, the principal reported, Chelliah transformed it from a third-rate to a first-rate school. He also established the Anglo-Chinese Continuation School for overaged students in Penang.

He was a mathematics wizard and graduated with a B.A. (Hons.) in Mathematics from the University of London in 1923, and obtained a postgraduate diploma in teaching in 1924.

He returned to Malaya and married Mary Ebenezer Rosalind Mani in 1925. They had six children. 

In June 1940, at the age of 46, he received his Ph.D in London, the first person to be awarded a Ph.D by a British university in the education service in the Straits Settlements and Malaya. His thesis, “A History of the Educational Policy of the Straits Settlements from 1800-1925", was a pioneering piece where he advocated the importance and need of bilingualism in education in Malaya. 

In 1941, he went to Singapore and became the assistant principal of St Andrew's School and later, vice-principal from 1946 to 1961. He also started the St Andrew’s Continuation School in 1946 to accommodate overaged pupils whose education was affected by the war.

In 1956, his dream for bilingualism came true when he started the Anglican High School with equal emphasis on Chinese and English in the curriculum.

In recognition of his service to education in the Straits Settlements he was awarded a JP by the Singapore government in 1954 and the OBE by King George VI in 1956. Chelliah retired from 50 years of service in education in 1961. 

As secretary of the Anglican Mission Schools’ Board, he was instrumental in guiding many of the mission schools in Malaya such as St Aidan's Church, Bahau and St David's School, Melaka. His passion for education took him back to South India where he built a school in Maruthakulam in memory of his beloved wife, Rosalind, who died in 1971. Chelliah was actively involved in the St George's Tamil Mission and was elected vice-chairman of the Tamil Diocesan Council (TDC) in Penang. 

Bishop B.C. Roberts appointed him as a Lay Reader in 1931 and he was ordained to the Diaconate of St. Andrew's Cathedral, Singapore in 1940. Though he did not go through formal theological training, he was found to be suitable for the ministry. 

During the Japanese Occupation, he was installed as the acting dean of St. Andrew’s Cathedral from 1943 to 1945, the first such appointment in the Diocese. He took charge of the cathedral when Bishop John Wilson and other Europeans were interned at Changi. One of his daughters, Mrs Leana Thambyah, said to this writer in October 2004, in Malacca: “Though he was better qualified academically than his colonial masters, on numerous occasions he was placed in an ‘acting position’ due to his colour and being born to the wrong ethnic group." He was also bypassed in the promotion due to political reasons.

After the Second World War, in 1947, Chelliah was elected to represent Malaya at the International Missionary Council Meeting (IMCM) at Whitby, Canada. He was also appointed president of the Federation of Christian Churches in Singapore.

On January 25, 1958, Chelliah was appointed the first Asian Archdeacon of Singapore and served until 1966. He was involved in the development of Anglican schools and churches in Singapore, which included Johor and Melaka, until 1964. He also served as Vicar of St. Paul's, Serangoon Road from 1961-1971 where he built four housing units at the back of the church for financial sustainability. 

In addition to his priestly ministry, Chelliah was also actively involved in various social services. He was one of the founders of the St. John's Home for the Aged and later became its chairman. He was also the founder and council member of the Inter-Religious Organisation of Singapore (IROS) from 1949 to 1979.

After the departure of Bishop Kenneth Sansbury, the Archbishop of Canterbury appointed Chelliah as the Vicar General in 1966. Chelliah later installed Bishop Chiu Ban It as the first Asian bishop of Singapore at St. Andrew's Cathedral, Singapore. 

On January 1, 1967, Bishop Chiu elevated Chelliah as Archdeacon Emeritus, the first such honour in the history of the Diocese. He wrote: “Few men can equal the record of our beloved in Christ, Devasahayam David Chelliah, Doctor of Philosophy, Clerk in the Holy Orders for the long and outstanding service which he had rendered to the Diocese as teacher (1911-1961), priest (from 1949) and as administrator. There are few high posts in all the three capacities that Dr Chelliah did not occupy. Whether it was a teacher, Headmaster, Diocesan Secretary for Schools, Honorary Priest, Vicar, Archdeacon or Vicar-General, he brought to it a wealth of experience and wisdom and occupied each post with distinction and honour."

Chelliah died in Singapore on April 2, 1979, aged 85.