Art Unwin wrote:
Where exactly does a photon come from and what does it consist of?
... its existence has not been verified as yet by it's capture!

Photons are quantized elementary particles in the standard
model. Every time you see something, like this posting of mine,
you are capturing the photons incident upon your retina.

Double slit experiments with photons have been performed
with a single photon which apparently can go through both
slits at the same time and interfere with itself on the
other side. Those photon detectors indeed can capture
individual photons.

Photons are quite often generated and detected within
particle accelerators.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com