http://www.direct.gov.uk/en/TravelAn...code/DG_070236

"Although failure to comply with the other rules of the Code will not, in itself, cause a person to be prosecuted, The Highway Code may be used in evidence in any court proceedings under the Traffic Acts (see 'The road user and the law') to establish liability. This includes rules which use advisory wording such as ‘should/should not’ or ‘do/do not’."

Face it, the authorities can write whatever they like into the Highway Code, then use it in evidence against us!