I can see the WWI military record from Australia - on the first page he says he has NO previous service, and also that he has two children (did he and Esther have children before the marriage or is the 1916 date for marriage wrong?)
May 4 1916: says no previous service (question 11)
page 34: he claimed on medical discharge (rheumatism) to have been invalided out of the British Navy in 1896.
These cannot both be true. It might be that he was lying about previous service when he signed up because he thought they wouldn't take him on if they knew he'd been invalided out before. Also, it's likely he snipped a couple of years off his age at some point - they wouldn't have taken him if he was too old, either.