On 30 January 1649, King Charles I of England took to the scaffold outside the Banqueting House in London’s Whitehall. He had requested two shirts to prevent himself from shivering from the cold, a reflex he thought could be mistaken for fear. He knelt in front of the crowd and placed his head on a block. Moments later, the axe fell.

Now, 371 years later, the pale blue vest worn by Charles during his execution is to go on display. “This undergarment would have been a good thing to wear in January because it is knitted silk, so it would have been a warm garment,” said Meriel Jeater, a curator at the Museum of London.

The silk vest is the star of an exhibition due to open in October that will look at public executions in London from 1196 to 1868. The latter date marks the last such execution – that of Michael Barrett, who was hanged for murder at Newgate prison after being found guilty of involvement in a bombing.

The vest is notable for its stains but whether they are the marks of a sticky end or the contents of a terrified king’s stomach remains unclear. “We have had tests done on them by forensics labs to try and work out if they are blood, but they were inconclusive,” said Jeater, noting that the stains fluoresce under UV light – as would be expected for sweat and vomit but not blood. However, experts suggested the passage of time may have changed the composition of the substances, she said.

A pair of gloves made of kid leather and pink silk said to have been worn by Charles I at his execution. Photograph: Museum of London/PA

The exhibition will also contain other effects of the “traitor” king, including gloves and a handkerchief. “We can’t absolutely prove they were there on the day, but that is the story that has been handed down with these things,” said Jeater, noting that many were passed down from people connected to Charles. For example, the vest is thought to have been given to the king’s physician.

The stories of others who were executed, and the impact on their families, will also be covered in the exhibition. “We are mapping execution sites and also places where bodies were gibbeted, so they are hung in gibbet cages as a warning against crime,” said Jeater.

London Bridge is well known as a site where the heads of traitors were displayed. “There were so many different places in London where you could encounter either an execution itself or the aftermath of that,” she said.

Those who witnessed executions will also be under scrutiny – from why they turned up to how they reacted. “They could be quite supportive to somebody who was being executed and throw flowers to them and shout ‘good luck’ and things like that,” said Jeater. “Or if it was a particular horrible crime that had been committed, they could totally vilify the person who was being hanged, and throw things, and swear and shout at them and boo and hiss.”