Now I getting confused.

are the schoolteacher and policeman the one and the same, or not ?
I would take a guess with the occupation , schoolteacher seems to fit more with this
Nicholas G T Salmon born 3 Oct 1798 bapt Jan 3 1799
Father Nicholas. Mother Barbara.
Have not found death of either parents.
Have image
Marriage 2 Oct 1796
Nicholas Salmon widwer married Barbara Harding widow.
Have image
1838. August 28th St Mary Woolwich
Elizabeth Barbara Salmon married Thomas Self.
Father Nicholas George Thomas Salmon schoolteacher
1861 RG9; Piece: 404; Folio: 84; Page: 15;
Thomas Self 38 plumber painter b London
Elizabeth Self 37 b Warwickshire
William N 10 b Woolwich
Thomas 7 b “
Henry G 4 b “
Walter C 2 b “
ELIZABETH LONG 13 niece b Woolwich
This matches the 1851, so it seems George is probably half brother to Elizabeth ( Barbara ) Self.