The man labeled "Viggot" is QM Alfred Olliver. The "unknown" man is Fireman John Thompson.
I think the man is Alfred Olliver. The resemblance between Oliver and Viggot forces us to look very closely and in this case we can see that Viggot's nose does not match that of the man on the Adriatic. His beard style is also a bit different.It could go either way. You add a mustache onto Viggot's 1921 photo and it's really, really close.
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Then again, Olliver is close too! My only drawback with it being Olliver is that Olliver's complexion and hair color seems a bit lighter than whomever is in the picture.
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Agree, John Thompson is my great uncle. I know the picture on the right, The reason it makes me think it is also john on the left is the fact that he has the same nose and prominent eyelids - my mother has this trait, as to a certain extend do I !