Wild theories about Stonehenge have been around since the Middle Ages.

One of the most bizarre explanations for its existence is that it is a spacecraft landing pad for an ancient alien species.

Now conspiracy theorists believe those aliens have returned, following the appearance of a mystery UFO just days before the Summer Solstice.

A black disc visited the Wiltshire monument, according to UFO Sightings Blog, hovering briefly over the stones. UFO expert David Clarke said of the recent sighting, ‘Totally unconvincing. Probably a bird’

A huge ‘flying saucer’ UFO visited the Wiltshire monument, according to UFO Sightings Blog, hovering for a short time over the stones before disappearing.

The site said, the UFO is black in colour and disc shaped,’ and described it as ‘medium’ size at around 20 to 30 feet (6 to 9 metres) across.

Stonehenge appears to be a favourite site for strange sightings by UFO hunters,

One of the moment famous sightings came out in recently declassified government documents described as ‘Britain’s X-Files’.

Stonehenge appears to be a favourite site for strange sightings by UFO hunters. One of the moment famous sightings (pictured) came out in recently declassified government documents described as ‘Britain’s X-Files’.

The files from 2007 to 2009 reveal several of bizarre reports of encounters with extraterrestrials.

Along with a UFO in Stonehenge, they include a man who claimed he lived with an alien and spaceship sightings near the Houses of Parliament.

The first description of a UFO was from a sighting made in US in 1947, although Met Office reports a quarter of a century earlier had included data on unexplained phenomena.

In 1952, Prime Minister Winston Churchill took the issue so seriously that he ordered reports of sightings to be kept secret to avoid public panic.

UFO expert David Clarke said of the recent sighting, ‘Totally unconvincing. Probably a bird.’

STONEHENGE WAS A ‘BOTCHED JOB BY COWBOY BUILDERS’

Cowboy builders botched Stonehenge and may have never even finished it, according to a leading historian.

Professor Ronald Hutton described the prehistoric wonder on Salisbury Plain, Wiltshire, as ‘a unique and possibly failed experiment – as much a triumph as a disaster’ in a talk at the Daily Mail Chalke Valley History Festival.

It is a triumph, he said, ‘because the darned thing’s still there and it’s the most famous prehistoric monument in the entire world’ built by somebody who was ‘insane enough to want to try the experiment of working enormous stones as if they were wood’.

‘They pulled it off but they had some bad times along the way,’ said Professor Hutton, an expert on paganism from Bristol University.

‘When they put up one of those great sandstone blocks in the outer circle, it slipped when it was being put in its hole, fell over and broke in half.’

Stonehenge is a prehistoric monument located in Wiltshire, England, about 2 miles west of Amesbury and 8 miles north of Salisbury