The EA will tell you if they are the statutorily appointed navigation authority for a stretch of river. If they are then it means that they control navigation on the river and can tell you the conditions under which navigation takes place.
Hmmm firing the gun without checking you have the right cartridges can lead to a blowback... Another misinterpretation of what I said, but I guess that suits your cause.
The EA's local offices are fully aware of which waterways and sections thereof have a PRN and will tell you, albeit there might well be an obscure bit of river where the rights (voluntary perhaps) have never been established, but they will be few on the ground. If you ask them who to seek permissions from to navigate the Grand Union Canal they will tell you the C&RT now. They're not stupid, but you won't ever have saught their advice I take it.
You see Mr Two Trucks, whatever is offered whether evidence or what, you don't want to believe it because it doesn't suit your purpose.
We anglers could play at that game (in fact it used to be played in olden times when communication was poor), but it would be pretty short lived these days. For us, it's known as poaching and if you do it at night there's an even greater suspicion that it's for stealing fish. Now you may think you're not stealing anything, but you are robbing the rights to a pleasure that anglers have paid for if you're not supposed to be there. You might say it's like the bus would go on its journey with or without me and without me there would just be an empty seat, but you try getting on it without paying and it's THEFT!
But what's the use, you're not going to listen to any reason whatsoever, like I said, anarchists. And if that upsets you, think about effects your actions have and don't be surprised by the abuse you will receive, sadly.