William DAY
 

Name - "official" name and what they were known as
William Day
Date and place of birth
Not known
Names of parents
Not known
Date and place of baptism - if applicable
Not known
Details of each of his or her marriages - if any
Married Elizabeth Mills on 15 October 1809 at St George in the East, Middlesex
Occupation(s) - if any
Clerk/accountant/West India dock foreman; possibly also owned a ship(if - big if - the family stories are true)
Addresses where they lived (including county if in UK) - and please list which censuses you have or haven't found him/her on (if s/he lived in census times!).
1810 - Ratcliff Highway, Stepney
1812 - Nelson Street, Stepney
1814 - 1816 Berner Street, Stepney
1818 Dog Row, Bethnal Green
Date, place and cause of death
Not known; he is 'deceased' on one daughter's marriage cert of Oct 1838 but not on another's in Jan of the same year so he might have died between Jan-Oct 1838. Or earlier - it's all a bit vague!
Date and place of burial.
Not known
Details of will / administration of their estate - if applicable
Not known
Memorial inscription - if any
Not known

I do know that ships were often owned by a consortium of people, so that the risk wasn't all taken by one person, so it could be that he owned a share of a ship or ships.

Yes, that's possible - there could be a grain of truth in it.

The second half of the story is that he sailed to Spain in it and brought back a Spanish wife which is going to be hard to prove!