Residing in Tetcott, Devon, England in 1775 but was not born there.
Year of birth, date of marriage, and date of death from Neville Richards, grandson of Ivy Grace Oliver. My earlier information had year of birth “before 1754”.

Place of marriage from Amy Utting’s family tree advised by email on 4 October 2018. Amy is the x3 great granddaughter of Francis Oliver b 1840.

Record of marriage Banns found in March 2021 in Marriage Banns Register Book:
Name: John Oliver
Event Type: Marriage Banns
Marriage Banns Published: 11 August 1771
Marriage Banns Published: 18 August 1771
Marriage Banns Published: 25 August 1771
Event Place: North Tamerton, Cornwall, England
Event Place (Original): North Tamerton, Cornwall, England
Sex: Male
Spouse's Name: Hannah Sleeman
Spouse's Sex: Female
https://www.familysearch.org/ark:/61903/1:1:NFLL-K...amp;treeref=MQTQ-HJZ
Note: Login to FamilySearch required

Record of marriage found in March 2021 in Marriage Register Book, England Marriages, 1538–1973
Name: John Oliver
Event Type: Marriage
Event Date: 7 Oct 1771
Event Place: North Tamerton, Cornwall, England
Event Place (Original): North Tamerton, Cornwall, England
Sex: Male
Spouse's Name: Hannah Sleeman
Spouse's Sex: Female
Solemnised In Presence Of: Oliver Sleeman [Bride’s Father]
Solemnised In Presence Of: Philip Brooke
England Marriages, 1538–1973
https://www.familysearch.org/ark:/61903/1:1:NFLL-P...amp;treeref=MQTQ-HJZ
Note: Login to FamilySearch required

Date and place of baptism, name of father, found in March 2021:
Name: John Oliver
Gender: Male
Baptism Date: 15 Jun 1740
Baptism Place: Ashwater, Devon, England
Father: John Oliver
FHL Film Number: 916805

Was John Oliver here married before his marriage to Hannah Sleeman?
Contributor, Katia, wife of Tim Grant Oliver, in an email dated 29 August 2021, located a marriage record dated 3 February 1761 for a John Oliver and a Margaret Ball in Ashwater, Devon, England (login required):
https://www.familysearch.org/ark:/61903/1:1:NKYM-3LX

(Tim Oliver is a x3 great grandson of James and Ruth Oliver, his grandfather being Ivor James Clark Oliver 1907-1989).

A burial document dated 3 June 1763 for Margaret with a husband of John Oliver was also found
https://www.familysearch.org/ark:/61903/3:1:S3HY-6...%2F1%3A1%3AQGNZ-74PX

The same burial document also lists a “John Oliver”, son of John and Margaret Oliver who was buried on 3 June 1763, three months earlier than his mother.

Further searching found a christening record for the son John. He was christened on 8 Oct 1761 in Ashwater, making him aged about 2 1/2 years when he died:
https://www.familysearch.org/ark:/61903/1:1:N5QS-1Y9

It is interesting to note that our John here (1740-1807) was born in Ashwater, making this discovery of a possible prior marriage in Ashwater, and a young son that was buried in Ashwater, very plausible. And, we know that John was 31 before his marriage to Hannah Sleeman in 1771. At the time of the possible first marriage to Margaret Ball in 1761 John would of been 21. With Margaret having died in 1763, John would not have remarried for just over seven years later. This does all seem very credible.

Confirmation of burial, occupation of Thatcher, from image of Tetcott burial record for of John Oliver, from contributor, Katia, wife of Tim Grant Oliver, in an email dated 12 July 2022:
“1807, December 9th, John Oliver, Thatcher, Aged 70”.

Image from Katia in same email of 12 July 2022 for “The Year 1760, Banns of Marriage between John Oliver, Thatcher, and Margaret Ball, both of this Parish were publifhed on the three Sundays underwritten:
That is to fay,
On Sunday the 21st of December by me P. Sherwin
On Sunday the 28th of December by me P. Sherwin
On Sunday the 4th of January 1761 by me P. Sherwin”
[Spelling using an “f” for an “s” as was the practise in those times]

Confirmation of marriage date and of John’s occupation from another Image from Katia in same email of 12 July 2022 for “1761, John Oliver, Thatcher, of this Parish and Margaret Ball, spinster of this Parish were Married in this Church by Banns this third Day of February in the Year One Thoufand Seven Hundred and Sixty one by me P. Sherwin Rector. This Marriage was Folemnized between us: John Oliver, The mark of Margaret Ball In the Prefence of John Glanvill, Anthony Downe”.

Confirmation of baptism date from another Image from Katia in same email of 12 July 2022, “Christings 1740, John son of John Oliver was Bapt June the 15th”.