It's a blue-ish/gray shape, and Gunn and his friends feel that it looks like a Roman soldier walking down the footpath on which the video was shot. The apparition vanishes as soon as two people jog through it. The image was, apparently, not visible to Mr. Gunn while he was present on site, but he saw it when reviewing his footage later that day.
Gunn has stated that he does not believe in ghosts, but that the image he captured seems strange, and has him curious. He also has stated that others have reported ghost sitings in the area, though he doesn't buy into those stories.
The only photo that I have been able to find of the alleged apparition is small, and of low quality, from the BBC News website:
I tried to find the unedited video, but could not, I did, however, find this version, with cheesy music and analysis:
Commentary: This story is, in of itself, not all that interesting. There's any number of things that could account for the image on the video - smoke, dust, even just an artifact of the camera itself. But as I read it, it got me thinking of something that I find significantly more fascinating - the evolution of the ghost photograph.
During the 19th century and through the mid-20th century, photographs with images claimed to be the apparitions of various spirits were common. Some of these images seem like obvious fakes to anyone looking at them now, while others are more subtle and require some knowledge of photography in order to figure out what they actually show. However, when photography was new, and people's eyes had not yet adapted to seeing photographic trickery, even the fake photographs might seem eerie and be taken as evidence of a spiritual presence.
Photo from www.real-ghost-pictures.com
The famous Brown Lady of Raynam Hall ghost photo.
A rather obvious fake, the Andrews Baby ghost photo.
What all of these photos have in common is that they all try to show a human form, eerily translucent or looking tormented, or even just "out-of-phase" looking. In an era before television and film special effects taught us what to look for in film trickery, and before Photoshop and digital cameras made us only too aware of the many easy ways in which even a rank amateur could fake a photo, those who wanted to show us spirits on film tried to make them look genuine.
Contrast the above photos with what we tend to get now: "orbs" and "streaks":
A rather typical and unimpressive "orb" photo from the forums at http://www.debunkingskeptics.com/
I looked for other "orb" photos, but they're all pretty much the same, so I figured I wouldn't bore you too much. The above photo is pretty typical, and just as unimpressive as the rest. The "orbs" and "streaks" so often used for ghost photos these days are actually a pretty easy-to-explain artifact of the cameras being used. Remember, a camera operates by bringing light in, and turning that light into an image, either on a photographic paper or through electronic sensors. Anything that reflects light will effect the image, and as cameras bring in light in a manner a bit different than how the human eye does, this means that objects may appear on film or in digital images that are not visible to the naked eye. Small objects that can reflect light (raindrops, motes of dust, insects, etc.) tend to reflect it in a spherical pattern that is not visible to the human eye, but does show up on camera. If the object is caught in a particular way or is moving quickly enough, this may show up as a "streak" rather than a sphere. Likewise, small light sources, maybe dim enough to not be noticeable to the naked eye, may show up on film as streaks if the camera or the object emitting the light is moving, even slightly, when the shot is taken. This is especially true in low-light conditions.
A photo of rain illustrating a point, from euroghost.eu
What the orbs and the streaks have over faked photos is that they are clearly genuine - anyone can get similar photos, and they don't have the hallmarks of special effects or image modification because they are, quite simply, real images really captured. They are also normal, non-supernatural things that show up in photos. So, spirit photography has really suffered, with people leaving behind outright fraud and instead settling for mediocre bad photography. It's rather like how early 20th century mediums would communicate complex messages from the spirits, while John Edwards appears to be playing a stupid game of charades (or, more likely, cold reading).
So, rather than being convincing evidence of the supernatural, orb and streak photos are evidence that even the early spirit photos tend to be fakes, otherwise we'd still be seeing their like rather than this dull silliness.
Sources: BBC News, Wakefield Express