A prime example of a screwed up restriction is to attempt to travel off peak between some stations west of London, such as Reading, and Norwich. In theory, the Network rule should apply.
However, on the outward leg, travel is prohibited on any train arriving in London before 10am, despite GA selling off peak London - Norwich tickets on the 9:30am departure from Liverpool Street. This means the earliest off peak arrival in Norwich from these stations is at 12:50.
It's just as screwed up coming back. Due to imposing a blanket evening restriction out of London Paddington the "heavily used" 14:00 departure from Norwich is classified as a peak train! Goodness knows how on-board staff choose to interpret this bizarre restriction - has anyone spotted a GA guard "upgrading" a passenger on this service to an Anytime fare?