The law is NOT there for “should” statements in the Highway Code. “Shoulds” are considered best practice, and can work against you in a careless/dangerous driving case if you didn’t follow them, but they are not themselves tied to any specific legislation. “Must” statements ARE backed up by legislation, and so can be enforced.
The highway code is not law.
Do you have something to back that up? It seems very odd that London would be named specially as must not then a second clause for the remainder of the country that sounds different. Surely it should either be “you must not park on the pavement” or if there’s some archaic reason that London needs specific wording "you must not park on the pavement in London, and you must not park on the pavement elsewhere "
Nope : rules in the Code which are legal requirements, and which you will be committing a criminal offense if you disobey, use the words “must/must not.” Violating other parts of the Code, which use the words “should/should not” or “do/do not”, can be used as evidence against you in Traffic Court, even if violating them is not an automatic criminal offense
If that were true, the text could read “ You MUST NOT park partially or wholly on the pavement unless signs permit it. “