One of the earliest eyewitness reports of a flying saucer in the modern era of the UFO phenomenon has been uncovered.

The typed account was made by a Barbara Graves who wrote from her home in Durban, South Africa, to friend Muriel Armfield in Chertsey, Surrey.

She described how on March 8, 1953 while taking a photograph of the Botanical Gardens in the coastal city she spotted a 'round object' that hovered high in the sky.

She insisted it was definitely not an aircraft.

Barbara told Muriel: "I hope you don't think I've taken to the bottle when I tell you that on Sunday, Tom and I saw a Flying Saucer over Durban.

"We were taking photographs...and Tom asked me to look up to get the sun on my face when I spied a round object in the sky, very high and moving.

"We both agreed it definitely wasn't an aeroplane - it was a perfectly cloudless, blue sky, otherwise we would never have seen it at the height it was.

"We watched it travel a good distance, and then it seemed to remain in the same spot for quite a long time - then went higher and higher until it was lost from our sight."

She then expressed her regret at not having a telephoto lens on her camera which might have captured the UFO.

At about the same time there were other similar sightings of a 'flying saucer' over South Africa.

Two South African Air Force flying officers reported seeing unidentified aerial objects above Durban on the same day Barbara reported hers.

Experts say that contemporary accounts from the formative years of the modern UFO phenomenon are 'astonishingly scarce' as people were often ridiculed for speaking out.

The letter is coming up for sale at Sworders Auctioneers of Stansted Mountfitchet, Essex, as part of their Out of the ordinary sale.

It was found inside a box of unrelated ephemera purchased at a flea market in the south west of England.

Mark Wilkinson, a spokesperson for Sworders, said: "The significance of this letter lies as it is a genuine surviving first-hand UFO eyewitness account written in 1953, at a time when such sightings attracted worldwide attention but were often met with scepticism and ridicule.

"No comparable private first-hand UFO eyewitness letter from this period is known to have notably appeared on the open auction market, making the survival of this document exceptionally rare.

"Personal letters of this nature were seldom preserved, with many lost or discarded over the years, and many witnesses choosing only to confide in trusted individuals rather than speak publicly.

"Its importance is further enhanced by the fact that, unknown to the writer, the same sighting was independently reported on the same day by two Air Force pilots, whose account was later preserved in a contemporary newsreel.

"Emerging from the early years of modern UFO investigation, this letter offers a rare insight into the personal and historical context of the 1950s UFO phenomenon."

The letter is tipped to sell for between £300 to £500 on August 18.