Rupert Castle-Smith, B Social 1906. Private, 15th Bn, Australian Imperial Force.  Believed to have been killed in action, Battle of Arras

He was reported missing on 11th April 1917, but not confirmed killed until December 1917.  He left school after just one year and went out to Australia soon after.

Aged 26

(CWGC lists him as Rupert Castlesmith)