 Complete the following phrase:  Campion was commissioned into the part-time 2nd Volunteer Battalion, Royal Sussex Regiment, later 4th Battalion, Royal Sussex Regiment of which his father was Honorary Colonel in 1888. On the outbreak of World War I he was the battalions senior Captain with the rank of honorary Major. He became Lieutet-Colonel of the 1st Line battalion 14th Royal Sussex and commanded it in the Gallipoli campaign. At its first action, at 