Leonard Henry Nelson Stephen OBE, MBE, later known as Henry Stephen, was born at 11 Dalton Terrace, Manchester on 10 July 1889 and baptised at St Mary's Church in Hulme on 10 July. He was the son of the printer John Stephen and Mary Eliza Owen, who were married in the Portsea district in 1888.

His younger brother James was born in 1892, but died the following year.

At the time of the 1901 census Leonard, as he was recorded, was one year old and living with his parents at 45 Wellington Street, Mosside, Manchester. His sister Florence Violet Stephen was born soon after the census.

By the time of the 1911 census, Henry (21) was a student, living at 98 Bland Street, Manchester with his father John (48), his mother Mary Eliza (46), and his sister Florence (10).

His father died in 1917.

Stephen studied at Victoria University, Manchester, where he received the Doctor of Science dgree in 1920. He served on the faculty at Victoria University, becoming a senior lecturer in 1921. At Manchester he worked with Chaim Weizmann (who became President of the State of Israel in 1949).

In 1921 at Haslingden, Lancashire, Henry Stephen married his first wife Edith Heyworth, and they had one child:

• James Henry Stephen (born in Manchester on 28 November 1925).

In 1925 Henry Stephen invented the Stephen reaction, a way to make aldehydes (R-CHO) from nitriles (R-CN): see H. Stephen, Journal of the Chemistry Society, 127, 1874 (1925). .

In 1926 he moved with his family to South Africa on his appointment as Professor of Chemistry and Dean of the Faculty of Science at Witwatersrand University..

His first wife Edith died Johannesburg in 1929.

He then married his second wife Theodora de Keiwet (known as Dora), by whom he had three children, Michael, Edith, and Richard.

In 1954 Stephen retired from Witwatersrand University, and in 1957 he returned to England. In 1957 he became the first editor of the chemistry journal Tetrahedron. The Stephens lived in Cumnor Rise

On 6 July 1965 Henry Stephen died in Oxford at the age of 75, and it was only on his death that the Headington connection came about. His widow Dora sold their Cumnor house and bought the land off Kiln Lane in Risinghurst (including the lake) that had been attached to C.S. Lewis’s house, The Kilns. She had a new house built for herself on part of this land (8 Lewis Close, next door to the Kilns).

The present nature reserve was then full of brambles, and the lake clogged with weeds, and in 1969 Dora Stephen gave this 12 acres of land to BBONT (the Berks, Bucks, and Oxon Naturalists’ Trust), which has since been renamed BBOWT (the Berks, Bucks, and Oxon Wildlife Trust). She wanted it named the the Henry Stephen Nature Reserve in memory of her husband, but eventually a compromise was reached and it was called the Henry Stephen/C.S. Lewis Nature Reserve. In 2003 the reserve was renamed the C.S. Lewis Reserve (In Memory of Henry Stephen).

Dora Stephen, who was also an eminent chemist, continued to edit the journal Tetrahedron until she retired at the age of 85. She sold her house on Lewis Close in about 2000 and died in 2006.

The nature reserve appears to have dropped the name of Henry Stephen altogether now:

• Berks, Bucks & Oxon Wildlife Trust: C.S. Lewis Nature Reserve
• Oxford Times, 12 June 2007: “Dispute over reserve’s name”