Most of the letters and poems are by Hester "Nessy" Heywood and younger brother Peter Heywood, and the transcription and reproduction of their correspondence and poetry may have been instigated by Peter as a lasting monument to his sister Nessy, who had devoted herself to him and his release when he was imprisoned on HMS Hector awaiting his court-martial in connection with the Mutiny on the Bounty, and had died very young.
Two are privately owned, the other three are in libraries: The Manx National Heritage copy consists of a preface page with the name of the owner, E. C. Fleetwood, whose wife Elizabeth was Nessy's niece, and several unbound small books and additional loose leaves which are numbered from 1 to 397, and which include a total of 184 different documents.
Most of the documents are dated between 1790 and 1793 and deal with Peter’s alleged participation in the Mutiny on the Bounty and the court proceedings against the mutineers.
Manx National Heritage obtained the Heywood Manuscript as well as letters and poems by Peter Heywood and returned them to the Isle of Man, when Bonhams in London auctioned off letters and manuscripts by members of the Bounty expedition in 1996.
A second inscription Aunt to Bessie Fleetwood Castle Lawn Douglas suggests that Mary left the manuscript to her niece Elizabeth Fleetwood, the daughter of Mary's and Nessy's youngest brother Edwin Holwell.