"There was a story of children chased out of a forest by a hairy ape man. One of them fell and and noticed the creature stopped the chase as soon as it fell. It just looked at them," he said. "Similarly, a group of youngsters were chased through a woodland near Sheffield by a six-foot-tall figure with red eyes."
McGrath, who authored the book "Beasts of Britain," is part of a small group of Bigfoot researchers in the U.K. He and his colleagues investigated alleged sightings of aggressive ape-like men, mysterious footprints, children running for their lives through woodlands and the sounds of trees crashing down as eerie groans echoed across the field. (Related: Unexplained "booming noises" baffles people around the world.)
These incidents allowed them to form a rough idea of what the British Bigfoot might look like. According to McGrath, the creature is no more than six feet tall and is more human-like than the U.S. version. It has a wide jutting jaw and brows, a low forehead and arched feet.
"Picture a Neanderthal, a large, hair-covered humanoid, and you're getting there," McGrath said.
The history of the British Bigfoot is related to the legend of the Green Man, he said, which is a hairy, man-like creature depicted in ancient art as a human face surrounded by leaves and represents the life cycle of the forest. It is also found in cultures across Europe, particularly in Germany and France.
The British Bigfoot has never been caught on camera before but a handful of people claim they saw the humanoid beast. Deborah Hatswell was a teenager when she witnessed what she described as a "huge, hairy, gorilla type-face" peeking out from the bushes in Salford, Manchester.
"It was a huge thing, like a man and an ape had been pushed together," she told The Face last January. "It had amber dark eyes, with dark brown hair, and yet it had a redness to it. Its jawline was thickly muscled, and its teeth were like a human's. His nose was flattish, like a boxer."
She was with a friend in the park when she caught a slight movement in the bushes and shadows. Upon seeing the terrifying figure, the two immediately leapt to their feet and made the run for it. Hatswell looked back and saw the creature lean back into the greenery "as if he'd melted away."
The now 52-year-old paranormal investigator has been searching for the British Bigfoot since the 1990s. She said that she has been obsessed with uncovering the truth of what she saw that day ever since the mysterious encounter.
"I still can't really explain what I saw. I didn't ask for it. I didn't wish for it," she said.
Paranormal theories supporting Bigfoot's existence suggest that the beast travels through time using a series of wormholes powered by the moon. This essentially allows the creature to disappear and evade searches. But McGrath is skeptical of such theories.
"I think that the portal theory is a throwaway explanation and we should be exhausting every line of enquiry on Earth before we get into the non-corporeal theories," he said.
He also clarified that the British Bigfoot is still hypothetical. As he noted in a warning about the danger posed by the creature: "If they exist, and it is a big IF, proceed very carefully."
Unexplained.news has more on mysterious sightings.