Appying the rules
Yesterday (or the day day before, depending on what day it is at the moment!) I flew from LAX to LHR with Virgin. A bit chaotic, one way and another, but pleasant enough over all.
BUT next to me was a luggage-bundle. She arrived with three carry-ons (large handbag, carrier bag of booty and limit-pushing carry-on bag, plus coat). The carry-on went into the overhead locker; the other bags more than filled the underseat space and the coat filled her lap.
On take-off, the cabin monitor for our chunk of plane asked her to put the coat under her seat - then passed on without a second look. Passenger (English far from fluent) took no action, and no-one came to follow up the instruction.
On landing, passenger tried to pass her blanket and pillow to the cabin monitor but was told to put them, and her coat, under the seat in front. No room there, so no action taken and no follow up.
Of course, the risks of a catastrophic crash at either point are small - but I assume the under-the-seat rule is there to keep escape routes clear, so surely it should be enforced more rigorously?