The connection between Plato Smith and Barthwell Smith has always troubled me slightly, as I’ve never been able to make a definitive link between the two.
The only tangible evidence between Plato and Barthwell I have so far been able to find is a work by Terrance Lee, dated 1995 titled “The Smith Gipsy Genealogies and Related Gipsy Families” which was found on the FamilySearch website (https://familysearch.org/) Page 91 of this work shows a family tree for a Plato Smith baptised 23 Nov 1806 in Rothwell, Northamptonshire. This shows he has a sister Brownetta Smith 1794 from Cold Higham, Northamptonshire. Showing, parents as Thomas and Nancy/Ann.
The Parish Records clearly indicate Brownetta Smith was baptised 9 Feb 1794 the daughter of Thomas and Nancy Smith, the very next page of this register shows Barthwell Smith baptised 21 Jun 1795, it has always struck me as odd that Barthwell Smith is missing from the work by Terrance Lee, but….

The next issue I had was trying to find any evidence that Nancy and Ann was one and the same person. Gipsy genealogy is notoriously difficult to work through and it is known for gipsies to use numerous names, Barthwell Smith is a prime example of this, using names like Matthew and various spellings of Barthwell, however I’ve never found any other link between Nancy and Ann.
The work by Terrance Lee also shows Plato Smith had numerous children with Maria/Mary, these include Neptune born 28 Mar 1819, John bap. 31 Mar 1822, Sius bap. 20 Apr 1828, Israel bap. 28 Dec 1830, Louisa bap. 24 Apr 1836, Maria bap. 26 Nov 1838, Isabel bap. 10 Feb 1844. These children were baptised/born in either Bedfordshire or Hertfordshire. Others may yet be found.

My problem with this is if you take Plato being baptised 1806, and his eldest son Neptune being born 1819, that would make Plato only 13 years old. Of course Plato may not have been baptised a baby but a young child although there is no evidence of this, and unless otherwise proven I find it best to take records at face value.
Looking back through the records we found a prison record for Plato Smith (https://apps.bedford.gov.uk/grd/detail.aspx?id=1843) the details given in this record show Plato Smith was male, 19 years old and 5ft 4in tall, it also identifies him as a gypsy. For the record he was charged with Riot and Violent Assault and sentenced to 7 days hard labour.
The interesting thing about the above record is Plato’s age 19 that would make him born 1798, a better age to father the above mentioned children, secondly and in my opinion more importantly was were this event took place, Felmersham in Bedfordshire, the children of Plato and Maria were all born either in Bedfordshire or Hertfordshire.
Further research has found a Plato Smith baptised 13 May 1798 the son of James and Jane Smith in Chelmsford, Essex.
Another record to add to the research is a burial record for Plato Smith in Broughton, Northamptonshire, this records states 18 Dec 1806 Plato Smith a gipsy child was buried.

Having studied Plato Smith for some time my conclusions are:
1: Plato Smith baptised 23 Nov 1806, Rothwell, Northamptonshire son of Thomas and Ann Smith, died as an infant and was buried 18 Dec 1806 at Broughton, Northamptonshire.
2: Plato Smith baptised 13 May 1798, Chelmsford, Essex son of James and Jane Smith, “married” a Maria and had the children listed above and in the work by Terrance Lee.

My final conclusion is that Plato Smith is the son of Thomas and Ann, Ann possibly being Thomas second “wife” and therefore Plato possibly being the Half Brother of Brownetta Smith and Barthwell Smith.

Of course this is still an ongoing piece of research and could change………………………………..