I've accidentally cycled on Westway and the West Cross Route, neither of which have motorway status any more but are forbidden to cyclists. However, if you get caught in the one-way system on Gloucester Terrace, that's where you end up. There is a prohibition sign for bigger lorries and buses, but not for bikes.
That's crazy.
That's exactly where I ended up on it. If there's no sign, any prohibition can't be enforced anyway.
I think part of the A40 on the approach to Oxford is No Cycling.
I have cycled on the forbidden bits of the A406 in the wee small hours.
None that I'm aware of. I've cycled the A40 from the Wolvercote to Denham at various times. There is a section of the A4142 that's signed as no cycling heading northbound from Horspath, cycling southbound from that junction was always good fun.
Actually going past a no cycling sign a little further along on the service road for the Mini plant, then immediately rejoining, only to exit for Cowley (you could stay on!). It was fun because you avoided most of the traffic flow, and could get some decent speed up down the Cowley exit.
Now, I did once end up on the M40 from Milton Common until I got back onto the A40 at Wheatley...
Anyway, regarding the Humber, it looks like at this angle you could avoid seeing the cycling restrictions.
"If you can't see it, it's not there!"