I think this episode serves as a succinct lesson of how credulous people can be. However, it also serves to highlight another important fact about how the eye and brain works. If we choose to accept that the photographer is not perpetrating a hoax, then we have to accept that this "object" was not visible when taking the picture. I would suggest that the reason it was not visible, is simply that the eye and brain was doing its job by filtering out superfluous information. When driving a car, you look through a windscreen, not at it. Any miscellaneous reflections are not consciously taken into account. This person was apparently not only driving but also using a cellphone to take pictures of the London scenery (well done there, for not killing someone). In those circumstances, I would suggest that the reflection of a real tiny luminous alien creature on the dash would have been ignored, too.

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This is not an idea to be tossed aside lightly - it should be thrown with great force