On the eve of the 400th anniversary of Sir Walter Raleigh’s execution for treason, a discovery at a medieval manor in Surrey may help solve the mystery of what became of his severed head.

A red silk velvet bag found in the attic of West Horsley Place, former home of Raleigh’s son, could have been used by Raleigh’s widow to carry around his embalmed head, according to the stately home and a historical costume expert.

Accounts of the beheading at the palace of Westminster, London, on 29 October 1618 record that the head was placed in a red bag, and that it and his body, wrapped in his nightgown, were taken away in a mourning coach by his widow.

Facebook Twitter Pinterest The bag found in West Horsley Place. Photograph: The Mary Roxburghe Trust

While the body of the soldier, poet, explorer and courtier is believed to have been buried in St Margaret’s Church in Westminster, the subsequent whereabouts of his head are less certain, according to historians. One biographer claimed his widow, Elizabeth, formerly Bess Throckmorton, a lady-in-waiting to Elizabeth I, had the head preserved in a case, while other accounts claim she kept it in a bag until her death at West Horsley Place, where she lived with her son Carew Raleigh and his family.

Mark Wallis, co-director of Past Pleasures costumed historical interpretation company, who inspected the bag at the manor this month, said: “It’s clearly a bag of the period. Whether it held the mummified head, I couldn’t say. But that Lady Raleigh lived there means that it’s much more likely than it would be otherwise.

“If it did hold the head it would have been when it was mummified, and not covered in blood and gore. I doubt this was the bag that Lady Raleigh took away from Whitehall where he’d been executed.”

The Mary Roxburghe Trust, which manages the manor, is commissioning further analysis of the bag, according to director Peter Pearce.

But historian Anna Beer, author of Patriot or Traitor: The Life and Death of Sir Walter Ralegh, cast doubt on the discovery, which she likened to other posthumous myths about Raleigh – such as those wrongly crediting him with introducing the potato to Britain and placing his cloak over a puddle for Queen Elizabeth.

“It’s almost definitely not the bag,” she said. “Almost every source on Raleigh’s execution has wonderful detail of the full horror of it, and that Lady Raleigh took his head away in a red leather bag.”

Although Beer said the widow might have used the mummified head as a visual aid to rehabilitate her husband’s reputation, she had not come across “any eyewitness account from the time of when Lady Raleigh whipped out her husband’s head”.

• This article was amended on 31 October 2018 to clarify that the execution took place at the palace of Westminster.