Fair point Tashengurt, in my defence back in the 80’s I spent just about all my tour on the SSA site and anything relating to traffic law that I learnt back then I have long forgotten! In those days anyone stopping anywhere along the A15 was regarded with suspicion, including aircraft spotters, and generally from inside the fence we were instructed just to tell them to move on. Of course it was all double yellow lines along the road and the parking area at the WAVE didn't exist.
The reference to a train crossing was because I assumed that the principles, if not the actual law, may be the same. Looking at the Highway Code does not seem to provide the answers and this link simply references vehicles.
https://www.gov.uk/government/upload...ng-traffic.pdf
I think it may be that a pedestrian going past the red flashing lights at a railway crossing commits a trespassing offence under the Railway by laws but it’s not clear if the same applies to a road. We clearly need an up to date proper policeman’s view here not some retired snowdrop!