My question is reading guidelines on speeding offences
Where have you read that?
just on AI internet searches on radar enforced variable speed limits and I thought also that it was a general guideline that the driver would be aware of the speed limit via visible means i.e. signage and/or other. my point being that in none of the photos is my car visible with a prevailing speed limit shown. however if this is enough for them to prove the case and there is no point me contesting then I will cop the COFP and move on with my life....? my point being that there is no photo showing my car and that gantry in the same shot. it is really difficult using the traffic in the opposite lane to judge where my car will have been in relation to the gantry, my guess is that I've just gone under the gantry (as per other reply) and it was the first one I have seen - I would have slowed sufficiently if there had been previous gantries illuminated. from what I have seen in replies so far I can then infer that it doesn't matter even if this is the first gantry on the motorway showing the speed restriction - there is no grace period for passing under it at over that limit...?
there is no grace period applicable in terms of them having changed suddenly - the timing on the photo says 19 mins and change 'since last change'.
unfortunately my stupid dash cam SD card didn't have enough memory on it and there journey has since been looped over as this would have been conclusive either way. I have now purchased a 512G card!!!