can a cyclist hop off their bike and walk across a junction if the lights turn red (and it is safe to do so!)?
Living in UK, I think we are lucky to live in a free country (free in the roads and pedestrians context as well as much else - try 'jaywalking' in other countries). In UK, with the exception of motorways, clearways and roads with the "No Pedestrians" sign displayed, I believe pedestrians can proceed legally on every public road in the country.
People walking/running (that's one foot after the other) are pedestrians, whatever they are pulling or pushing.
Meanwhile we know (from Crank v Brooks) that a person pushing a bike is a "foot passenger" (pedestrian)
(Crank v Brooks [1980] RTR 441)
Extract (from upthread): "In my judgment a person who is walking across a pedestrian crossing pushing a bicycle, having started on the pavement on one side on her feet and not on the bicycle, and going across pushing the bicycle with both feet on the ground so to speak is clearly a 'foot passenger'."
. . . having stopped on your bike in the road, getting off and pushing it across the road doesn't feel right.
Having stopped on your bike, if you then push it onto the pavement then push it across the road with other pedestrians feels much better
I agree with both those statements. Also, reading the appeal court judgement, the cyclist inferentially does not become a pedestrian until they've stepped (ie both feet on) onto the pavement, not astride their bike. But once they've done that (and stay on their two feet), they are a pedestrian and have all the legal freedoms and limitations afforded to a pedestrian. And I think the judgement would have merit in any pedestrian in the road situations (not just on a pedestrian crossing).
The Highway Code has a
section for pedestrians and (besides motorways(+) prohibition) has a couple of 'MUST NOTs': "You MUST NOT loiter on any type of crossing." "You MUST NOT cross or pass a stop line [of railway level crossings] when the red lights show, (including a red pedestrian figure)."