If you are going to hoax a diamond shaped UFO, you'd add the vertices facing the observer. Yet no such vertices are actually visible. The object then gets reduced to being two cones....one inverted on the other...and not a 'diamond' at all.
Why posit that the hypothetical hoaxer was trying to make a diamond-shaped UFO?
The UK MoD referred to it as diamond-shaped, but they might have simply been referring to the 2D outline (like the diamonds in a deck of cards).
Two shallow cones base-to-base sounds like quite a stereotypical UFO to me!
I agree with your point made earlier that the "diamond" isn't particularly symmetrical, although also accepting that a reflection in water need not be (my feeling is that it isn't a reflection, but I don't have evidence to support this, other than the foreground of fence and dangling foliage which we're all familiar with- I suspect they're real and the "right way up", but can't prove it).
But there is then the further problem that the UFO must surely be angularly above the observer, which means the rim of the UFO ought to curve upwards slightly in the centre. Yet that rim is totally straight implying seeing an object directly side on. This really does not make sense...as it would imply that the horizon is where the UFO is, or the UFO just happened to be conveniently tilted downwards, and I very much doubt that.
Part of what I would describe as asymmetrical is the "midline" between the two differently shaded/ coloured halves of the diamond. It seems (to me) to travel from each outer edge, angled slightly upward to meet at a dark spot just right of the (approx.) vertical axis, possibly an indication it's
not being viewed exactly side on.
(I then go down a rabbit hole of my own digging: )
I sketched this out (below) wondering if there were vertices between the dark spot and the (approx.) corners of the diamond:
(The lower sketch I've "lifted" the point with the dark spot to make my supposition a bit clearer).
My impression was that the dark spot might be the nearest point of a roughly octahedral body. If that were the case, there would be vertices. I was toying with the idea that the object might be a real military item, perhaps a radar reflector of similar topology to, but flatter than, ones we're familiar with,
e.g. a reflector for small boats, another near the tail of a badly-damaged TDU-10 Dart towed aerial gunnery target,
[one of the photos of Dart wreckage at
Vegas Hikers.com, where there are some specs as well.]
-but covered with a skin- maybe the whole thing being a lightweight inflatable containing an octahedron of e.g. Mylar reflecting panels stretched between a lightweight frame.
Hypothetical purposes: A towed cheaper alternative to the TDU-10 Dart and similar targets; a towed test rig for radar absorbent materials; an experimental radar decoy.
Not particularly hi-tech, but possibly sensitive.
In my reverie, I entertained thoughts of a floating inflatable on a
very long line frightening the witnesses- that old thing about time seeming to pass more slowly during fright- suddenly to be jerked away as the circling jet takes up the slack.
Or maybe it slipped its line and was being followed by the planes (tug and observer), "popped" and the sudden upward movement of a piece of skin distracted the witnesses from falling debris which ended up, like at Roswell, as so much foil and mangled struts in a farmer's field. -All rather unlikely I guess.
Unfortunately for me, on checking through the original Calvine thread I found most of this had been discussed before,
starting with
@NorCal Dave here, with hon. mentions to
@JMartJr,
@Duke, and
@DavidB66 in subsequent posts.
And as for the vertices, I'm unsure if I really see indications of them or if it's pareidolia on my part, or visual noise from a possibly mottled or rough-surfaced object.
So much for all that.
But I don't feel that the angle of the "UFO" to the observer necessarily shows it to be real, a fake UFO, or a non-UFO related item. There are photos of UFOs at various angles (all of which I'm confident are fakes); equally there are photos taken from the ground of real aircraft viewed side-on.
The biggest issue with the object in the picture is the bright left "wing"—it just doesn't fit.
I'm thinking that the plane in question is likely to be a Harrier. The strange lightness of the left wing could be explained because the Harrier's wings have significant anhedral. In other words, one has a flatter angle to the camera than the other, reflecting more light.
-And I gave some examples in
post #870.
Maybe not a good analogy but here's my take on the "Colorado Phoenix", which I believe is an airliner partly reflecting the setting sun (the witnesses had gone outside to watch the sunset

):
Aviation enthusiasts tend to try and get clear pictures showing the form and "natural" colours and markings of their subjects, so photos in books, online etc. are a bit self-selecting.
The Calvine photo is not a clear picture. We don't know what the "diamond" and "jet" are.
But we do know David Clarke's photography friend at Sheffield Hallam University, who went to some lengths in analysing the photo, described the jet as being consistent with a Harrier, and that defence officials who saw the six original negatives "established" it was a Harrier, and that another aircraft was "probably" a Harrier.
We don't have the evidence the defence staff saw, or know what examination took place, but we know that evidence existed.
(I think it's probably a model).
I'm no expert on Harriers, but can they really fly at such a slow speed while banking?
I think that's a very good point; the instructor in the video implied that transition to a hovering regime starts at 120 knots, but for all I know that might require level forward flight. I've seen Harriers "bow" in the hover (bring the nose slowly down then up again) but not tilt laterally as far as I can recall. Although Harriers have puffer jets near the wingtips, nose and tail, the main nozzles only rotate in the vertical plane (parallel to the aircraft's length).