Also on the above webpage:

Why is pavement parking a problem?

"Pavements are constructed and provided for pedestrian use. Vehicles parked on pavements are:

a hazard to pedestrians causing an obstruction which may result in them having to step off the pavement onto the highway thus putting themselves in danger
a hazard by restricting the width of the pavement making it difficult for someone with a pushchair or wheelchair to pass safely - again this person may have to step into the highway to avoid the obstruction
a hazard due to the damage caused by driving on and off the pavement - e.g. broken flags."

Of course it is a compromise. The clue is "Pavements are constructed and provided for pedestrian use". The easiest/cheapest way for the council to deal with the issue of pavement parking is this fudge. Just because it is legal doesn't mean it is not a compromise. There is a big assumption here that the pavements should be rebuilt (at considerable cost) for parking. One day, under more enlightened policy, the pedestrians might get their pavements back. If they are dug up now that will be less likely to happen.