I agree with both John and William
As Ricky Tomlinson would say "Commander RN" My A***
John
at the marriage of John and Rebecca 15th. July 1840 at Deal
John is a sailor of Lower Street, father is William a Dyer
Rebecca's father is John Goodchild, a waterman.
John signed, but Rebecca marked.
None of that seems like a prelude to being a commander in the R.N.
Also - commanders of R.N vessels get their name in the paper a lot.
The only McKown who seems to do that is a Captain in the Royal Artillery
So - Yes the Commander in the R.N. is poppycock
I think he is using the adult baptism on 18th June 1880, father John a commander in the R.N. to establish some credentials.
Interestingly his address is Sarah Brisley's (Cossington House, Rocky Hill)
So I have the impression of a suave young man on the make. Seeing an opportunity to get some money from a widow.
Such that he was prepared to marry Martha who was 6 years older than he.
It is interesting that at the marriage it is William Augustus who gives his address as Cossington House while Martha's is Aylesford. He is really in with the aunt!
I know this is repetition but just to outline my thinking -
in 1888 we know William Augustus is in the Liverpool area (from newspaper re his bankruptcy)
in 1891 the trustees for his bankruptcy are still trying to sort things out and one of them, Mr Sumner, lives in Liverpool
So the 1891 census entry found by John fits in very well and as already commented upon is a nice transition to a later birth date and different place of birth.
In addition his initials have been reversed.
Someone who is W.A. (or A.W.) McKOWN can not thereafter be found
But in 1896 W.A. Wellesley McKOWN shows up relating to the hotel at Oban
then all the rest as already given
1906 court case to do with Mabel. (No Wellesley in that piece)
1907 Mabel dies and Dorothy is sent off to Canada.
1908 marriage
1910 - the skating rink
1910 - the British-Austrian Oil Investment Company Ltd
with the addition that in 1917 he was living in Essex, but I cannot find that entry now.
Anyway
If you could find William Augustus Wellesley-McKOWN before 1891
or William Augustus Mckown after 1891 then of course they would be two different men.
But that does not seem to be the case. One follows on from the other.
I agree the 1908 marriage is well worth getting
and I would like to see if Sarah Brisley made any comments in her will. It seems likely to me that she would if she was leaving anything to Martha, as she would want to prevent it getting into William's hands.