Captain George William Valentine Clements 1st (Royal) Dragoon Guards died 3 March 1916 aged 85. He is acknowledged as the oldest soldier to die in uniformed service in WW1 and is buried in Norwich Cemetery.
https://www.cwgc.org/find-war-dead/casualty/2803091/clements,-george-william-valentine/ Thank you Cynthia Budd
Anne IWM Volunteer commented
A page has been created here for him https://livesofthefirstworldwar.org/lifestory/7696549. Thanks for reporting