Shades of grey: What is the brocken spectre?
A spooky weather effect, which in the past was thought to be a supernatural creature, has been photographed in the Scottish mountains. But what is the story behind the brocken spectre?
The myth describes him as a Scottish Big Foot, said to loom large in shifting grey cloud on the UK's second highest mountain.
The Big Grey Man of Ben Macdui first came to prominence in the 1920s during a dinner speech at an annual gathering of the Cairngorm Club in Aberdeen.
Its honorary president, the highly respected mountaineer Prof John Norman Collie, told of a frightening experience on Ben Macdui in the Cairngorms 35 years earlier.
Prof Collie was climbing alone in snow and mist when he heard crunching sounds, as if he was being followed by something large and ominous. Prof Collie turned and fled.
Another climber A M Kellas, a lecturer and veteran of Himalayan ascents, later told Prof Collie of similar terrifying experience on the Scottish peak.
Other mountaineers came forward to say they had not just heard but seen the Big Grey Man.
The sightings have a scientific explanation called the brocken spectre.
The phenomenon was recently photographed on Meall a Bhuiridh in Glen Coe by a Sportscotland Avalanche Information Service (SAIS) forecaster.
It was during a period of inversion when the mountain tops were poking up through low cloud and mist.
According to the Met Office, the brocken spectre effect is produced when a person stands above the upper surface of a cloud - on a mountain or high ground - with the Sun behind them.
"When they view their shadow the light is reflected back in such a way that a spooky circular 'glory' appears around the point directly opposite the Sun," the Met Office said.
The spectre can often appear larger than the person observing it, giving the impression of some kind of giant grey creature.
The term brocken spectre originates in Germany. The Brocken is the highest peak in the Harz Mountains.
There was a listening post on the summit during the Cold War when the mountain formed part of East Germany.
The Brocken is cloud or mist-covered for 300 days a year, according to travel website Germany is Wunderbar, and wrapped in old superstitions and fairytales involving witches.