| Regimental number | 56421 |
| Place of birth | Northam Western Australia |
| Religion | Church of England |
| Occupation | Station hand |
| Address | Subiaco, Western Australia |
| Marital status | Single |
| Age at embarkation | 20 |
| Next of kin | Father, H Withnell, 18 Kershaw Street, Subiaco, Western Australia |
| Enlistment date | 11 April 1918 |
| Rank on enlistment | Private |
| Unit name | Western Australian Reinforcement 2 |
| AWM Embarkation Roll number | 23/111/2 |
| Embarkation details | Unit embarked from Albany, Western Australia, on board HMAT A74 Marathon on 29 July 1918 |
| Rank from Nominal Roll | Private |
| Unit from Nominal Roll | 6th Field Artillery Brigade |
| Fate | Returned to Australia 12 July 1919 |
| Miscellaneous details (Nominal Roll) | *Sidney spelt Sydney |
| Family/military connections | Brother: 8074 Pte Algy John WITHNELL, 11th Bn, killed in action, 19 July 1918. |
