When World War II erupted, Manuel joined the Royal Australian Air Force and once again served his nation.
He swore that he was a natural born British citizen, that he worked as a farmer, and that his uncle, Frederick George Jones, was his next of kin.
He scored his first aerial victory on 2 April 1918, in company with Captain Henry Garnet Forrest; they destroyed a German two-seater reconnaissance machine over Demuin.
Two months later, on 2 June, he destroyed two Pfalz D.III fighter planes, then drove down a third one out of control within the half hour.
[6] British military intelligence later exhumed this German pilot's body to examine the parachute he was wearing.
[8] Manuel returned once again to farming, and would continue to foster aviation in northern Australia;[8] he flew until shortly before his death.
[5] Lt. Roby Lewis Manuel (Australian Flying Corps) During the past month, whilst on an offensive patrol, his machine was badly damaged in an encounter with an enemy aeroplane which he brought down out of control.
By skilful manoeuvre he completely defeated the enemy in a combat that only lasted twenty minutes, at the expiration of which period only four hostile machines remained in the air, and these retired.