His journals would become famed for their vivid detail and candour. But now, almost exactly 360 years after diarist Samuel Pepys chronicled the Great Fire of London, new research has found that he “erased” and “curated” correspondence to conceal he had been offered an enslaved boy as a bribe.

Cambridge University historian Dr Michael Edwards consulted hundreds of records in The Pepys Library at Magdalene College, Cambridge; The National Archives; and the Bodleian Library in Oxford for the study “Samuel Pepys, the African Companies, and the Archives of Slavery, 1660–1689”.

One of the most unsettling details of the study, published in the Historical Journal, concerns the offer of a human bribe to Pepys, a senior naval official in the 1670s.

Edwards, a fellow of Jesus College, Cambridge writes how, in April 1675, John Howe, a naval officer, sought to win Pepys support in his case that he had been wrongly deprived of a ship’s command after the death of its captain.

Howe wrote to Pepys to “crave your acceptance” of a “small” enslaved boy, which “I brought home on board for your honour … Hoping he is so well seasoned to endure the cold weather as to live in England.”

Pepys wrote back indignantly rejecting the offer. But Edwards argues this was not because of ethical concerns about slavery, but the optics of looking like a man who could be bribed.

In order to protect Pepys’ reputation, Edwards argues the boy’s story is reduced to mentions of a “gratuity” or “reward” in parts of his archive – and so his fate disappears from the record. At the time, Edwards says, enslaved African boys were in demand as servants, and an offer of this kind “wasn’t unusual”.

“Pepys is quite a kind of compulsive archive maker. He preserves lots of his naval papers.

“But if you look at the language of the way he writes these letters (about this incident), he stops talking about a boy and stops talking about a person.

“He’s not concerned about the ethics of enslavement in the way we would be – he’s worried about concerns that he’s been tempted, so he uses that language of reward and gratuity because those are kind of official words.

“He wants to show that he’s acting by the book. Trying to exercise control over how people perceive him does seem to be quite important to him. We know he takes other forms of bribes.”

Edwards says Pepys’ clerk, William Hewer, indexed and organised the correspondence in way that preserved Pepys’ innocence was preserved while the enslaved child’s history was “erased”.

He added: “Pepys … had good reason to be cautious. As Secretary to the Admiralty, he was running one of the biggest parts of the state in this period. The Navy involved enormous amounts of money and was highly politicised. Pepys had lots of political enemies and a few years later, in 1679, he was imprisoned in the Tower of London, after charges of corruption and popery.”

Pepys’ work arranging the loan of naval ships to the Royal African Company’s (RAC) including for the trade in enslaved African people, formed the backdrop to the incident, Edwards says.

Howe, the man who offered the bribe to Pepys, had been a naval officer on the ship Phoenix, which Pepys had arranged to be lent to the RAC before it took enslaved people from Africa to Barbados, arriving in November of that year. The ships log records the deaths of 19 enslaved people, all of whom were thrown overboard.

Elsewhere in his archives, Pepys speaks of his links to enslavement unashamedly. In September 1688, he told a ship’s captain that neither “whipping or fetters” had reformed a “mischievous” enslaved man in his household, telling the captain to feed the man on “hard meat, till you can dispose of him in some plantation as a rogue”.

Meanwhile in 1679 Pepys arranged to sell an enslaved male through another naval contact, whom he told: ‘Pray not my black-boy add any thing to your care.”

Neither of the men, or the boy referred to in the records were named.

Edwards said: “The English state in this period and the crown are deeply entangled with enslavement in lots of different ways. The presence of substantial amount of Black people in London in the 17th century and all of those things are part of the story of the development of England as a global power.

“Pepys had so many connections within England’s African trading companies as well as in the Navy. This part of the story has gone mostly untold.”