I have an ancestor who I presumed was in the RN in WW1. He was torpedoed in an armed merchant cruiser on Icelandic patrol. Now I have heard that his Continuous Certificate of Discharge book means he was a merchantman, possibly under RN orders. As he volunteered or was conscripted in 1917 and was discharged in 1918 I find it unlikely he was not in the RN. He was listed as being in HMS Sunhill which I think was a Liverpool training ship; HMS Champagne (torpedoed); and then HMS Eagle before he was discharged "per Ministry of Shipping Order" Has anyone any ideas or experience of this scenario, please?