In message , Christian
Hansen writes
I often wear a small backpack, but take it off when boarding buses or Tube
trains. These packs are too big to remove and carry.

There are rules against bicycles at certain times of day and on certain lines.
Why not a "Backpacks must be carried" rule?
In the 60s and early 70s you weren't allowed on the tube "as opposed to
subsurface" unless you could carry it. Cycles and prams were not
allowed under any circumstances regardless of the reason.
--
Clive.