In article m, Martin
Underwood writes
It seems to me that this advice is rather naive, because it assumes that
the only impediment to the "car in front of you that's also waiting to
turn right" is the flow of oncoming traffic - which will eventually
stop. What if the real reason that the car in front can't turn right is
a traffic queue on the road to the right. In that event, both of you
will be "marooned" in the middle of the box junction when the lights
change :-(

Isn't the situation that you describe covered by the "are only stopped from
doing so by oncoming traffic, or by other vehicles waiting to turn right"
clause - the implication being that you must not enter the box if anything
*else* prevents you completing the turn - for example the fact that traffic
on your right is backed-up as far as the box.

I think you need a crystal ball. Imagine you are the first of the right-
turning cars. The road to the right is clear (at least one space to turn
into). But the oncoming traffic prevents you turning. And then an
oncoming car turns left, and fills up that space you used to have. Are
you suddenly a criminal? The same for the next car back, observing (if
indeed the sight-line is unobstructed) that there are spaces for two
cars in the road to the right, initially.
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